THE   PRINCIPLES   AND    PRACTICE 


OF 


IRON  AND  STEEL  MANUFACTURE 


BY  THE  SAME  AUTHOR. 

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LONGMANS,     GREEN,     AND     CO., 
39   PATERNOSTER    ROW,    LONDON. 

NEW    YORK,    BOMBAY,    CALCUTTA,    AND    MADRAS. 


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THE  PRINCIPLES  AND  PRACTICE 


OF 


IRON  AND  STEEL 
MANUFACTURE 


BY 

WALTER   MACFARLANE,    F.I.C. 

PRINCIPAL  OF  THE  STAFFORDSHIRE  COUNTY  iMETALLURGICAL  AND   ENGINEERING 

INSTITUTE,  WEDNESBURY 

PAST  PRESIDENT,  STAFFORDSHIRE   IRON  AND  STEEL  INSTITUTE 

FORMERLY  BURSAR  IN  TECHNICAL  CHEMISTRY,   ANDERSON'S  COLLEGE 

ASSESSOR  IN  METALLURGY,   ROYAL  TECHNICAL  COLLEGE,    GLASGOW;    AND 

VICE-PRESIDENT  WEST  OF  SCOTLAND  IRON  AND  STEHL  INSTITUTE 


.tfiftb 


LONGMANS,     GREEN,  AND     CO. 

39   PATERNOSTER   ROW,  LONDON 

NEW   YORK,    BOMBAY,    AND  CALCUTTA 

1917 


-r 


PREFACE. 


THE  author  of  this  book  was  for  fourteen  years 
engaged  on  the  technical  staff  of  iron  and  steel  works, 
a  fact  which  may  account  for  the  attention  given  to 
practical  details  throughout  its  pages.  The  intention 
is  to  provide — as  far  as  the  scope  of  the  work  permits — 
sound  instruction  and  reliable  information  for  technical 
students,  metallurgists,  engineers,  and  others  engaged  in 
the  various  branches  of  the  iron  and  steel  trades. 

In  plan  the  book  differs  from  others  on  the  subject. 
Hitherto  it  has  been  usual  to  consider,  firstly,  the  iron 
ores,  and  then  the  several  processes  for  the  production 
of  finished  articles.  The  author  has,  however,  found  it 
better  to  begin  with  a  consideration  of  the  finished 
products,  as  they  are  more  simple  in  composition  and 
much  more  familiar  than  the  ores.  Some  years'  experi- 
ence of  each  system  has  convinced  the  author  that  the 
new  method  is  superior  to  the  old.  But  as  each  chapter  is 
self-contained,  the  reader,  student,  or  teacher  may  follow 
either  plan  without  inconvenience. 

The  plant  illustrated  and  described  is  in  use  in  well- 
conducted  works  at  the  present  day. 

Several  chapters  have  been  revised  by  acknowledged 
experts  having  intimate  practical  experience  of  their 
branches  of  manufacture.  To  friends  who  so  kindly 
helped  in  this  direction  the  author  is  grateful.  He 
desires  to  thank  the  firms  from  whom  he  had  permission 
to  take  works  photographs,  and  also  the  firms  to  whose 
generosity  he  is  indebted  for  sketches,  blocks,  &c. 


VI  PREFACE. 

Thnnks  are  tendered  to  the  Councils  of  the  Institution 
of  Mechanical  Engineers,  the  Iron  and  Steel  Institute 
(London),  the  Staffordshire  Iron  and  Steel  Institute,  the 
West  of  Scotland  Iron  and  Steel  Institute,  and  the 
Cleveland  Institution  of  Engineers;  also  to  the  Editors 
of  Gassier  s  Magazine  and  the  Foundry  Trade  Journal 
for  permission  kindly  granted  to  copy  extracts  from  their 
publications. 

Special  thanks  are  due  to  Professor  A.  Humboldt 
Sexton,  and  to  Messrs.  Alfred  Harvey,  Westminster; 
Joseph  H.  Harrison,  Middlesbrough ;  and  Robert 
Buchanan,  Birmingham,  for  valuable  suggestions. 

THE  MUNICIPAL  SCIENCE  SCHOOL, 

WKDNESBURY,  February,  1906. 


PREFACE  TO   THE   FIFTH  EDITION. 

A  FEW  alterations  have  been  made  in  the  text,  arid  new 
matter  has  been  added. 

STAFFORDSHIRE  COUNTY  INSTITUTE, 
WEDNESBURY,  Sept.  1917. 


CONTENTS. 


CHAPTER  PAOR 

I.     Introduction,  .........         1 

II.     Preliminary  Considerations, 3 

III.  The  Puddling  Process  for  the  Production  of  Wrought 

Iron, 11 

IV.  Crucible  Cast  Steel, 35 

V.     Treatment  of  Tool  Steel,          .         .         .         .         .         .51 

VI.  Mild  Steel, 57 

VII.  Acid  Bessemer  Plant, 64 

VIII.  The  Acid  Bessemer  Process, 75 

IX.  The  Basic  Bessemer  Process, 84 

X.  Acid  Siemens  Plant, 97 

XI.  The  Acid  Siemens  (Open-hearth)  Process,        .         .         .116 

XII.  The  Basic  Open-hearth  Process, 127 

XIII.  Bessemer  and  Siemens  Steel  Ingots,         .         .         .         .134 

XIV.  Mechanical  Testing  of  Steel  and  Iron 142 

XV.  Foundry  Practice — Iron  and  Steel  Castings,  .         .         .148 

XVI.  Malleable  Castings, 167 

XVII.  Case-hardening, 171 

XVIII.  Iron  Ores  :  their  Composition,  &c.,          ....  174 

XIX.  Preparation  of  Ores  for  Smelting, 182 

XX.  The  Blast  Furnace  and  its  Equipment,    ....  188 

XXI.  Working  a  Blast  Furnace, 203 

XXII.  The  Products  of  the  Blast  Furnace,         .         .         .         .213 

XXIII.  Notes  on  Fuels,  Fluxes,  Kefractory  Materials,  &c.,        .  224 

APPENDIX. 

Analyses  of  Finishing  Materials  and  Softeners,     ....  237 

Table  of  Various  Grades  of  Pig  Iron, 239 

Typical  Analyses  ot  Pig  Iron, 240 

Composition  of  Scotch  Pig  Iron, 241 

Composition  of  Cleveland  Pig  Iron, 241 

Analyses  of  British  Iron  Ores, 242 

Analyses  of  Bilbao  Ores, 243 

Analyses  of  Mediterranean  Ores, 244 

Analyses  of  Bricks, 246 


V11I  CONTENTS. 

PAGE 

Analyses  of  Gases, 246 

American  Iron  Ores, 247 

American  Ore  Supplies,           ........  258 

Modern  Hoisting  Machinery, 251 

Handling  Pig  Iron  at  Blast  Furnaces, 253 

Mixers, .         .254 

Tilting  Furnaces,    ...                  255 

Charging  Machines, 256 

Electrical  Applications, 257 

Syllabus  of  "Iron  and  Steel  Manufacture/''  City  and  Guilds  of 

London  Institute,    . xiii 


LIST   OF   ILLUSTRATIONS. 


FHJ.  NO.  PAGJi 

1.  Puddling  Furnace,  General  View,        .         .         .         .         .14 

2.  ,,  Longitudinal  Section.     .         .         .         .15 

3.  ,,  Plan,      .         .         .         .         .         .         .15 

4.  ,,                 Crosa  Section  through  Grate,          .         .  16 

5.  „                             ,,                  ,,        Fettling,     .         .  16 

6.  Charging  a  Puddling  Furnace,     ......  19 

7.  Pig  Iron  in  Puddling  Furnace,     ......  20 

8.  Puddler  Rabbling  a  Charge, 21 

9  Drawing  Puddled  Ball  from  Furnace,           ....  22 

10.  Tapping  Cinder  from  Furnace,     ......  24 

11.  Helve, 29 

12.  Steam  Hammer, 30 

13.  Forge  Train  (Mill  for  Puddled  Bars), 31 

14.  ,,            End  View, 32 

15.  Merchant  Bar  Mill, 33 

16.  Cementation  Furnace,  General  View,           ....  36 

17.  „                      Section, 37 

18.  „                     Plan, 38 

19.  Crucible  for  Steel  Melting, 42 

20.  Steel-melting  House,  General  View, 43 

21.  ,,             Hole,  Section, 44 

22.  Bessemer  Converter, 65 

23.  Tuyere  for  Converter, 66 

24.  Arrangement  for  Ramming  Converter,         ....  67 

25.  Bessemer  Ladle,  &c., 69 

26.  Ingot  Mould, 70 

27.  Steel-work  Cupola 72 

28.  Mounted  Ladle  for  Hot  Metal, 73 

29.  Pouring  "  Metal"  into  a  Converter, 75 

30.  Bessemer  Converter  while  Blowing, 78 

31.  Pouring  Metal  from  a  Converter,         .....  76 

32.  Steel  Ingot  and  Dogs, 77 

33.  Arrangement  for  Ramming  Basic  Plug,        ....  88 

34.  Bogey  Ladle  Crane, 89 

35.  Charging  Lime  into  a  Bessemer  Converter,  .  .         .90 

36.  Wilson  Gas  Producer,  Section, 98 


X.  LIST   OP    ILLUSTRATIONS. 

PIG.   HO.  PAGE 

37.  Wilson  Gas  Producer,  \vith  Water  Bottom,         ...       99 

38.  „  ,,             with  Discharging  Screw,  .         .         .101 

39.  Duff  Gas  Producer, 102 

40.  Siemens  Open-hearth  Furnace,  Front  View,         .         .  104 

41.  „  „                    Longitudinal  Section,          .     106 

42.  „  „                    Cross  Section,      .         .         .108 

43.  „  ,,                    Back  View,         .         .         .109 

44.  Siemens  Casting  Pit,  with  Ladle, Ill 

45.  Large  Steel  Ladle 112 

46.  Tapping  a  Siemens  Furnace,        .         .         .         .         .         .114 

47.  Peel  for  Charging, 116 

48.  Men  Charging  Steel  Furnace, 117 

49.  Steel  and  Slag  being  Tapped  from  Furnace,        .         .         .118 

50.  Teeming  Steel  into  Ingot  Moulds, 119 

51.  Stripping  Steel  Ingots, 120 

52.  Empty  Steel  Ladle 121 

53.  Neutral  Rib  in  Basic  Steel  Furnace, 129 

54.  "Feeding"  a  Steel-melting  Furnace, 130 

55.  Steel  Ingot  in  Course  of  Cooling, 135 

56.  Reheating  Furnace, .     137 

57.  Gjers' Soaking  Pit,      .         .        .         .        .         .        .        .139 

58.  Soaking  Furnace,          ........     140 

59.  Flat  Test  Piece, 142 

60.  Cylindrical  Test  Piece, 143 

61.  Foundry  Cupola  with  Solid  Bottom, 151 

62.  „  „  Drop       „ 152 

63.  ,,  ,,              ,,           ,,         Section,       .         .         .     153 

64.  „  ,,  „      Receiver, 154 

65.  Roots'  Blower, 155 

66.  ,,  Section, 155 

67.  Moulder's  Hand-shank  Ladle, 157 

68.  „         Double  Hand-shank  Ladle,  .         .         .         .157 

69.  „         Geared  Crane  Ladle, 158 

70.  „         Ladle  on  Wheels, 159 

71.  Chill  Casting, .         •         -163 

72.  Iron  Casting, 164 

73.  „  1«4 

74.  „ 164 

75.  „  164 

76.  „  164 

77.  „  165 

78.  Annealing  Furnace  for  Malleable  Castings,          .         .         .168 

79.  Scotch  Calcining  Kiln, 186 


LIST   OP    ILLUSTRATIONS.  ti 

ne.  NO.  PAGE 

80.  Gjers*  Calcining  Kiln, 186 

81.  Range  of  Iron-smelting  Blast  Furnaces,        ,         .         ,         .189 

82.  Modern  Blast  Furnace, 191 

83.  Scotch  Tuyere, ,         .         .         .194 

84.  Staffordshire  Tuyere,  .                           194 

85.  Lloyd's  Spray  Tuyere 194 

86.  Cast-iron  Hot-blast  Stove,   .                  197 

87.  Cowper's         ,,              „ 198 

88.  ,,                ,,              .,       Plan, 199 

89.  Blast-furnace  Pig-bed, 208 

90.  Grey  Pig  Iron,  Fracture 218 

91.  Mottled  „                ,,              -2 IS 

92.  White     „                ,,              218 

93.  Grey  and  White  Pig  Iron.  Fracture, 218 

94.  Front  of  Boilers  Fired  with  Blast-furnace  Gas,    .         .         .  222 

95.  Arrangement  for  Utilising  Blast-furnace  Gas— Section,       .  223 

96.  Gas  Engine, 223 

97.  Transport  Car  with  two  Charging  Buckets,        .         .         .  251 

98.  Charging  Bucket  at  top  of  Blast  Furnace,    ....  252 

Tilting  Furnace, Frontispiece,. 

Bogey  Ladle  Crane,       ......         facing  page,  89 

Crane  Locomotive,        .         .         .         .         .         .                  ,,  111 

Map  showing  the  British  Iron-making  Zones,       .                  ,,  180 

Blast-furnace  Hoisting  Plant,       ....                  „  251 

Overhead  Crane  with  Comb „  253 

Tilting  Furnace, „  255 

Charging  Machine, „  156 

Charging  Machine, „  257 

Electric  Furnace, „  258 

Babcock  &  Wilcoi  Boiler 221 


THE  PKINCIPLES  AND  PBACT1CE 


OF 


IRON  AND  STEEL  MANUFACTURE. 


CHAPTER  I. 
INTRODUCTION. 

IRON  is  the  most  plentiful  and  most  useful  of  the  metals. 

In  what  a  variety  of  useful  forms  do  we  daily,  hourly,  meet 
with  it !  In  stately  steamships,  whose  records  of  capacity  and 
of  swiftness  constitute  one  of  the  marvels  of  our  time;  in 
the  powerful  locomotive  careering  along  the  iron  way;  in 
machinery,  ponderous  and  powerful,  or  nimbly  delicate  and 
deft ;  in  hammer  and  anvil,  in  cannon  and  shot :  the  pen,  the 
sword,  the  ploughshare,  and  a  thousand  things  more,  from  the 
proverbial  "needle  to  an  anchor,"  are  fashioned  for  us  from 
this  most  useful  metal.  Our  terrible  battleships  with  their 
tremendous  guns  and  engines  are  composed  mostly  of  iron. 
The  newest  world's  wonders  have  iron  for  their  backbone. 
The  stupendous  bridge  which  spans  the  Forth;  the  Eiffel 
Tower,  of  "  solid  yet  graceful  construction,  which  rears  aloft 
its  fairy-like  form,  an  elegant  example  of  scientific  powers  and 
the  imaginative  genius  of  French  engineering,"*  and  the 
Tower  Bridge  have  become  possible  because  of  progress  in 
iron  (or  mild  steel)  manufacture. 

The  New  World  also  abounds  in  stupendous  structures  of 
steel  and  ironk  The  magnificent  bridge  at  Poughkeepsie,  the 
*  Sir  James  Kitson,  Bart.,  M.P. 


2  JPON    A>P    STeftL    MANUFACTURE. 

splendid  span  of  ^ll-nigh  1,600  feet  in  the  Brooklyn  Bridge, 
the  Williamsburg  and  other  bridges  at  New  York,  the 
majestic  bridge  over  the  St.  Lawrence  at  Quebec,  the 
towering  buildings  in  the  chief  cities,  the  appliances  and 
plant  for  dealing  quickly  with  a  gigantic  turnover  of  materials 
— all  these  attest  the  usefulness  of  iron  and  steel. 

Iron  is  extensively  used  for  so  many  purposes,  not  only 
because  it  is  abundant,  but  because  of  its  adaptability  to  a 
great  range  of  requirements.  It  can,  with  comparative  ease, 
be  caused  to  enter  into  chemical  union  with  other  substances 
with  most  remarkable  results. 

Wrought  iron  is  pliant,  tough,  and  reliable.  Mild  steel  is 
strong  and  flexible,  and,  like  wrought  iron,  can  be  hammered, 
rolled,  or  drawn  into  serviceable  shapes,  and  can  be  welded. 
With  more  carbon  in  its  composition,  medium  steels  suited  for 
other  purposes,  such  as  rails,  axles,  and  wheels,  are  produced, 
while,  with  still  more  carbon,  tool  steel,  which  can  be  hardened 
and  tempered,  is  made.  Who  can  count  the  service  to 
civilisation  rendered  by  tool  steel  ?  Iron  with  still  more 
carbon  is  adapted  to  the  formation  of  castings  of  utility  and 
beauty. 

When  iron  is  alloyed  with  such  metals  as  chromium, 
manganese,  nickel,  or  tungsten,  its  range  of  usefulness  be- 
comes vastly  extended,  and  if  articles  consisting  mostly  of 
iron  are  subjected  to  modified  heat  treatment  during  manu- 
facture, wonderful  additional  strength  and  endurance  are 
developed. 

In  its  magnetic  properties  iron  is  unique  among  the 
metals. 

Because  it  has  been  endowed  with  so  many  good  qualities 
in  well-balanced  proportion  IRON  is  the  MASTER  METAL. 


CHAPTER  II. 

PRELIMINARY  CHEMICAL  CONSIDERATIONS: 
DEFINITIONS. 

THE  great  gaseous  envelope — the  atmosphere — which  sur- 
rounds the  globe  we  inhabit  is  made  up  chiefly  of  two  gases, 
called  oxygen  and  nitrogen,  in  proportion  nearly  approaching 
to  4  measures  of  nitrogen  to  1  measure  of  oxygen.  There  is 
also  a  vast  amount  of  oxygen  in  the  rocks  and  minerals  which 
compose  the  crust  of  the  earth. 

Oxygen  is  the  active  agent  in  the  atmosphere.  When 
oxygen  enters  into  chemical  union  with  fuel  in  our  furnaces 
a  high  temperature  is  created,  by  which  the  extracting, 
refining,  and  working  of  metals  are  effected.  Its  chemical 
symbol  is  0. 

To  extract  iron  from  ore  a  high  temperature  is  necessary, 
and  if  a  mass  of  chemically  combined  iron-and-oxygen,  or 
iron  oxide  (which  forms  the  essential  constituent  of  our  iron 
ores),  is  brought  into  contact  with  carbon,  or  substances  which 
contain  much  carbon  (such  as  charcoal,  coal,  coke,  or  carbon 
monoxide),  at  a  high  temperature,  the  oxygen  leaves  the  iron 
and  unites  with  the  carbon  to  form  gases  which  ultimately 
find  their  way  into  the  atmosphere.  The  oxide  of  iron  is 
reduced  to  the  metallic  state  when  that  transfer  of  oxygen 
takes  place. 

For  the  extraction  of  iron  we  require  ore  containing  iron ; 
we  need  substances  (fuel)  which  will  combine  readily  with 
oxygen  and  evolve  a  high  temperature,*  and  we  must  also 
have  substances  which  withstand  chemical  action  even  at  a 
high  temperature.  The  latter  constitutes  the  refractory 
materials  with  which  our  furnaces  are  lined.  Associated 
with  the  iron  oxide  in  the  ores  we  find  other  matters 

*  Electricity  generated  from  water  power  places  n»  to  some  extent 
in  an  independent  position  with  regard  to  this. 


4  IRON    AND    STEEL    MANUFACTURE. 

(gangue)  such  as  sand,  lime,  clay,  &c.  Fluxes  are  required 
to  cause  such  substances  to  melt  more  readily  and  so  become 
fluid  at  the  furnace  temperature. 

Three  substances  have  already  been  mentioned — namely, 
oxygen,  iron,  and  carbon.  Each  is  an  element.  An  element 
is  a  substance  which  has  not  been  split  up  into  other  sub- 
stances. It  has  not  been  found  possible  to  transmute  or 
change  any  element  into  another.  There  are  about  7  8 
elements  known,  and  with  the  advance  of  science  the  number 
is  from  time  to  time  added  to. 

Each  metal  is  an  element :  no  one  metal  can  be  changed 
into  another.  Copper,  for  example,  cannot  be  changed  into 
tin ;  tin  cannot  be  changed  into  copper,  or  zinc,  or  any  other 
metal.  But  two  or  more  metals  may  be  melted  together  so  as 
to  form  an  alloy  differing  in  its  character  and  qualities  from 
the  metals  of  which  it  is  composed. 

There  are  other  elements  which  are  not  metals.  When  a 
non-metal  enters  into  union  with  a  metal,  or  when  two  or 
more  non-metals  unite  chemically,  a  compound  is  formed. 
Compounds,  too,  differ  in  character,  or  properties,  from  the 
elements  of  which  they  are  composed.  For  example,  a  piece 
of  iron  left  exposed  is  attacked  by  chemical  compounds  in  the 
air  and  is  changed  into  iron  rust.  The  brown,  powdery  rust 
differs  from  the  bright,  solid  metal. 

The  elements  to  be  considered  in  this  book  are  not 
numerous. 

Iron  (the  Latin  name  for  which  is  ferrum)  is  designated  by 
the  symbol  Fe.  It  is  a  metal  of  great  chemical  activity — -one 
which  is  so  quick  to  combine  with  substances  which  come  into 
contact  with  it  that  it  is  difficult  to  prepare  in  a  state  of 
purity.  Chemically  pure  iron  is  scarce  and  costly,  and  is  not 
of  commercial  importance. 

Three  oxides  of  iron  are  known  : 

(a)  Ferrous  oxide,  a  compound  in  the  proportion  of  one 
atom  of  iron  with  one  atom  of  oxygen.  It  is  therefore 
represented  by  the  chemical  symbol  FeO. 


PBELIMINAEY    CHEMICAL   CONSIDERATIONS.  5 

(b)  Ferric  oxide,  a  compound   in  the   proportion  of  two 
atoms  of  iron  with   three   atoms  of  oxygen.     Its  chemical 
symbol  is  Fe903. 

(c)  Magnetic  oxide,  a  compound  in  the  proportion  of  three 
atoms  of  iron  with  four  atoms  of  oxygen,  and  represented  by 
the  chemical  symbol  Fe304.     It  has  magnetic  properties. 

The  student  should  make  a  point  of  seeing  and  handling 
samples  of  iron  ores  containing  these  oxides. 

Arithmetically,  the  iron  oxides  ma,y,  for  purposes  of  com- 
parison, be  represented  thus : 

Ferrous  oxide,  .  .  FeO  or  Fe6O6 
Magnetic  oxide, .  .  Fe304  or  Fe608 
Ferric  oxide,  .V  .  Fe203  or  Fe609 

Ferrous  oxide  is  eager  to  absorb  oxygen  and  become  con- 
verted into  ferric  oxide.  If  ferric  oxide  is  heated  strongly  it 
loses  oxygen  and  is  changed  into  magnetic  oxide. 

The  chemical  symbol  for  carbon  is  C.  Carbon  and  oxygen 
enter  into  chemical  combination  with  each  other  in  two  well- 
defined  proportions,  forming  either  carbon  monoxide  or 
carbon  dioxide.  In  the  former,  the  proportions  are  one 
atom  of  carbon  to  one  atom  of  oxygen,  the  resulting  com- 
pound having  the  formula  CO.  In  the  latter  the  pro- 
portions are  one  atom  of  carbon  to  two  atoms  of  oxygen,  the 
resulting  compound  being  correctly  represented  by  the  formula 
CO,. 

When  abundance  of  air  is  present  in  a  furnace  which  is 
hot  with  glowing  fuel  containing  carbon,  the  carbon  becomes 
oxidised  (or  to  use  the  every-day  term,  " burned ") 'to  its 
fullest  extent,  and  carbon  dioxide  (CO^)  is  formed.  But  if 
the  air  supply  is  limited,  the  carbon  dioxide,  on  coming  into 
contact  with  more  hot  carbonaceous  fuel,  is  reduced  to  carbon 
monoxide  (CO).  The  following  equation  represents  the 
reaction : — 

C02  +        C        =  2CO 

Carbon  dioxide  and  carbon  yield  carbon  monoxide.  , 

Carbon    monoxide  is    very  useful   in   many  metallurgical 


6  IRON    AND    STEEL    MANUFACTURE. 

operations,  because,  at  ordinary  furnace  temperatures,  it  readily 
unites  with  oxygen,  as  indicated  by  the  equation — 

2CO  +       02  2C02 

Carbon  monoxide  and  oxygen  yield  carbon  dioxide. 

The  importance  of  these  statements  will  be  apparent  on 
reading  the  following  chapters. 

Chemical  combination  .takes  place  in  definite  proportions — a 
number  of  atoms  of  one  element  entering  into  chemical  combination 
with  a  definite  number  of  atoms  of  another  element. 

Each  element  has  a  relative  value  with  regard  to  each  other 
element ;  or,  to  state  the  fact  in  other  words,  each  element  has 
its  own  exchange  value  or  equivalent.  And  there  need  be  no 
more  mystery  in  the  exchange  value  of  an  element  than  there 
is  in  the  common  fact  that  1  shilling  is  equivalent,  or  of 
equal  value,  to  12  pence,  or  that  1  pound  equals  20 
shillings. 

The  exchange  values,  or  atomic  weights,  of  the  elements 
already  named  are: — Carbon,  12;  oxygen,  16;  iron,  56. 

12  Ibs.*  of  carbon  unite  with  16  Ibs.  of  oxygen  to  form  28 
Ibs.  of  carbon  monoxide ;  12  Ibs.  of  carbon  unite  with  twice  16 
Ibs.  of  oxygen  to  form  44  Ibs.  of  carbon  dioxide.  The  former 
is  represented  as  CO,  the  latter  as  C02.  72  Ibs.  of  ferrous 
oxide  (FeO)  contain  56  Ibs.  of  iron  and  16  Ibs.  of  oxygen.  80 
Ibs.  of  ferric  oxide  contain  56  Ibs.  of  iron  and  &£  Ibs.  of 
oxygen.  Ferric  oxide  might  therefore  be  represented  as 
Fe014.  But  to  obtain  the  most  simple  formula  for  ferric 
oxide  we  must  double  each  element  and  represent  ferric  oxide 
as  Fe203.  For  similar  reasons  magnetic  oxide  is  represented 
by  the  formula  Fe304.  The  iron  and  oxygen  in  magnetic 
oxide  exist  in  the  proportion  of 

Iron,        3  times  56  parts,  by  weight. 
Oxygen,  4      „      16     „  „ 

The  elements  to  be  considered  in  the  earlier  chapters  of 
this  book  and  their  symbols  and  equivalent  values  are — 

*Any  other  weight  may  be  substituted  for  Ibs.,  but  that  one  weight, 
or  unit,  must  be  kept  throughout  a  comparison  or  calculation. 


PRELIMINARY    CHEMICAL    CONSIDERATIONS. 


METALS. 

NON-METALS  OR  METALLOIDS. 

Name. 

Symbol. 

Atomic 
Weights. 

Name. 

Symbol. 

Atomic 
Weights. 

Iron,     . 

Fe 

56 

Carbon, 

C 

12 

Manganese,  . 

Mn 

55 

Hydrogen, 

Nitrogen, 

H 

N 

1 
14 

Oxygen, 

0 

16 

Phosphorus, 

P 

31 

Silicon, 

Si 

28 

Sulphur, 

S 

32 

The  chief  constituents  of  our  fuels  are  (a)  carbon,  (&) 
hydrogen,  and  (c)  compounds  of  carbon  and  hydrogen.  The 
heat  effects  of  their  combustion  are  dealt  with  in  Chapter 
xxiii. 

SILICON. — This  is  an  element  of  much  interest  to  iron  and 
steel-makers.  It  is  easily  oxidised.  The  only  known  oxide 
of  silicon  is  called  silica  and  has  the  formula  Si02,  which 
means  that  each  atom  of  silicon  has  entered  into  chemical 
union  with  two  atoms  of  oxygen;  or,  to  express  the  same 
truth  in  another  way,  chemical  combination  has  been  effected 
in  the  proportion,  or  ratio,  of  28  parts  (say  28  Ibs.)  of  silicon 
with  twice  16  parts  (say  32  Ibs.)  of  oxygen. 

Pure  white  sand,  or  quartz,  may  be  taken  as  fair  examples 
of  silica — the  oxide  of  silicon.  Silica  is  the  most  plentiful 
substance  in  the  earth's  crust.  All  iron  ores,  as  got  from 
the  earth,  contain  silica.  In  the  process  of  extracting  iron 
from  ores  some  of  the  silica  is  caused  to  part  with  its  oxygen, 
and  the  silicon,  thus  freed  by  reduction,  associates  with  the 
metallic  iron.  In  refining  the  iron,  in  subsequent  stages, 
such  silicon  requires  to  be  removed. 

MANGANESE  is  a  metal  the  oxides  of  which  are  frequently 
found  in  iron  ores.  Metallic  manganese  is  a  constituent  of 
irons  and  steels.  The  readiness  with  which  it  combines 
chemically  with  oxygen,  and  with  sulphur,  is  a  most  useful 
quality  which  is  freely  applied  in  steel-making. 

IKON,  when  pure,  is  a  silver-white,  tough  metal  which  can 
show  the  peculiar  brightness  known  as  metallic  lustre.  Its 


8  IRON    AND   STEEL   MANUFACTURE. 

melting  point  is  very  high.  When  melted,  or  even  heated 
highly,  where  air  has  free  access  to  it,  the  metal  becomes 
oxidised — that  is  to  say,  oxygen  unites  with  the  iron  forming 
a  crumbling  mass  of  "  burnt  iron."  Pure  iron  (a  very  rare 
substance)  is  more  .easily  burned  or  oxidised  than  impure  iron ; 
a  fact  which  can  be  understood  when  it  is  remembered  that 
the  impurities  usually  present  in  ordinary  iron  are  more  easily 
oxidised  when  hot  than  iron  itself  is. 

The  worst  impurities  in  many  manufactured  iron  masses 
are  sulphur  and  phosphorus. 

SULPHUR  tends  to  produce  red-shortness  in  iron.  The  term 
"  red-short "  means  that  it  is  brittle  when  at  a  red  heat. 

PHOSPHORUS  tends  to  produce  cold-shortness  in  iron,  the 
term  "  cold-short "  meaning  that  the  mass  is  brittle  when 
cold  ;  that  is,  at  ordinary  temperature. 

SILICON  in  certain  proportions  was  formerly  believed  to 
induce  both  red-shortness  and  cold-shortness,  but  recent 
researches  have  shown  that  silicon  cannot  be  classed  among 
the  highly  injurious  elements. 

Iron  or  steel  which  is  burnt,  or  is  red-short  or  cold-short,  is 
brittle  and  unreliable.  Burnt  iron,  or  iron  which  is  red-short, 
cannot  be  welded — at  least  not  in  a  satisfactory  manner. 

Although  there  are  objections  to  the  use  of  iron  or  steel 
containing  certain  proportions  of  silicon,  sulphur,  or  phos- 
phorus, it  must  be  kept  in  mind  that  presence  of  these 
elements  in  proper  proportions  is  beneficial.  For  example, 
some  mild  steels  containing  a  little  over  one-tenth  of  a  per 
cent,  of  sulphur  roll  into  sheets  better  than  some  makes 
of  purer  steel.  Certain  cast  irons  may  be  strengthened  by 
judicious  addition  of  sulphur.  Pig  iron  containing  a  notable 
amount  of  phosphorus  is  more  fluid  than  purer  pig  iron, 
and  so  takes  a  sharper  impression  in  the  mould  in  which 
it  may  be  cast. 

The  common  elements  which  are  usually  present  in  mild 
gteel — if  not  in  undue  amount — increase  the  power  of  the 
steel  to  resist  rupture  by  stress. 

Arsenic,  copper,  and  other  elements  were  formerly  looked 
on  with  disfavour,  or  were  held  to  condemn  the  steel  which 
contained  them,  but  experiments  carried  out  on  a  practical 


DEFINITIONS.  9 

scale  in  works  amply  disproved  the  notions  held  by  inspecting 
engineers.  The  marvellous  qualities  imparted  to  steel  by  the 
prudent  introduction  of  chromium,  nickel,  manganese,  tungsten, 
molybdenum,  and  other  metals  have  proved  most  helpful  to 
all  classes  of  engineers.  The  amount  of  carbon  which  is 
combined  with  iron  has  most  marked  effects  on  the  nature  of 
the  steel  produced  by  such  combination. 

There  are  certain  qualities,  or  properties,  possessed  in  a 
marked  degree  by  iron  and  steel  which  may,  with  advantage, 
be  defined  here. 

Malleability. — The  quality  which  enables  a  substance  to 
withstand  hammering,  rolling  out,  dishing,  or  flanging,  without 
being  cracked  or  broken. 

Extensibility  is  the  term  applied  to  the  stretching  which 
takes  place  before  rupture  when  a  metal  is  subjected  to  a 
pulling  force  in  a  testing  machine,  or  which  may  take  place 
when  the  metal  is  in  use  as  part  of  a  structure. 

Elongation  is  the  term  used  to  denote  the  act  of  lengthening, 
or  the  length  to  which  a  metal  has  been  stretched  by  the 
testing  machine. 

Elasticity  is  the  power  which  enables  a  metal  to  resume  its 
original  form  on  being  released  from  a  force  tending  to  alter 
its  form.  Thus,  a  piece  of  tempered  steel  may  be  considerably 
bent,  but,  by  virtue  of  its  elasticity,  it  will  straighten  itself 
when  released  from  the  bending  force.  A  piece  of  steel  may 
be  stretched  to  a  slight  extent,  and  its  elasticity  will  enable  it 
to  return  to  its  original  length  when  freed  from  the  power 
which  stretched  it.  If,  however,  the  stretching  is  carried  to  a 
certain  further  point,  the  limit  of  elasticity  is  reached,  per- 
manent set  occurs,  and  the  piece  of  steel  cannot  go  back  to  its 
original  dimensions. 

Ductility. — The  quality  which  enables  a  metal,  or  an  alloy, 
to  hold  together  and  conform  to  intended  shape  when  subjected 
to  squeezing  and  stretching  while  being  drawn  into  wire.  In 
practice  the  wire  is  drawn  through  a  series  of  holes,  which 
dimmish  in  size,  one  by  one,  in  a  draw  plate.  Sometimes  a 
metal  which  rolls  out  well  is  spoken  of  as  ductile. 

Tenacity*  is  the  quality  which  enables  a  substance  to  hold 
*From  the  Latin  tenax  =  to  hold. 


10  IRON    AND    STEEL    MANUFACTURE. 

together  when  subjected  to  a  force  which  tends  to  stretch  it. 
In  Britain  the  tenacity,  or  tensile  strength,  of  a  metal  is 
generally  computed  in  tons  per  square  inch  of  section,  in 
America  in  pounds  per  square  inch,  while  on  the  European 
Continent  it  is  usual  to  state  the  tensile  strength  in  kilo- 
grammes per  square  millimetre.  Mild  steel  is  more  tenacious 
— has  greater  tensile  strength — than  wrought  iron.  In  other 
words,  mild  steel  will  remain  unbroken  under  a  tensile  stress, 
or  pull,  which  would  rupture  wrought  iron.  For  information 
regarding  the  mechanical  testing  of  metals  see  Chapter  xiv. 

Toughness  is  that  quality  which  enables  a  substance  to 
withstand  oft-repeated  bendings  or  twistings  without  breaking. 

Welding  is  the  operation  by  which  wrought  iron,  and  the 
milder  varieties  of  steel,  may  be  firmly  joined  by  placing 
clean  ends  together  and  hammering  or  pressing  while  the 
pieces  are  at  a  proper  temperature.  Wrought  iron  is  at  the 
correct  temperature  when  in  a  plastic  condition. 

In  a  brisk  fire,  which  is  urged  by  a  blast  of  air  from  a 
bellows  or  a  fan,  the  iron  pieces  which  are  to  be  welded  are 
heated  till  white  hot.  The  surfaces  are  apt  to  be  more  or  less 
oxidised  or  "burnt,"  and  the  oxidised  particles  must  be 
removed.  Some  sand  is  therefore  thrown  over  the  white-hot 
parts  in  order  to  flux  off  the  oxides  of  iron.  Sand,  as  already 
explained,  is  essentially  silica  (Si02),  which  has  a  strong 
affinity  (or  liking)  for  ferrous  oxide  (FeO),  and,  although 
neither  of  these  substances,  separately,  could  be  melted  at  a 
temperature  far  above  that  of  the  white-hot  iron,  they  readily 
combine  with  each  other,  at  a  moderate  temperature,  to  form 
a  compound  (ferrous  silicate  =  2FeO,  Si02)  which  easily 
melts  and  flows  off,  carrying  with  it  the  ferric  oxide  (Fe203), 
and  leaving  clean  surfaces  to  be  welded. 


11 


CHAPTER  III. 

THE  PUDDLING  PROCESS  FOR  THE  PRODUCTION 
OP  WROUGHT  IRON. 

WROUGHT  iron  possesses  many  valuable  qualities.  It  is 
strong,  tenacious,  tough,  malleable,  and  ductile;*  it  possesses 
that  remarkable  and  valuable  property  which  enables  it  to  be 
welded.  It  is  not  altogether  free  from  the  slag  'which 
accompanies  its  production,  but  even  that  is  an  advantage,  as 
it  enables. arrows  structure  to  be  developed,  and  this  fibrous 
structure  hinders  dangerous  crystallisation.  For  certain  im- 
portant purposes  it  is  unsurpassed,  and  it  commands  a  higher 
price  than  is  paid  for  mild  steel.  For  these  and  other  reasons 
its  manufacture  continues,  although  its  practical  extinction 
was  prophesied  many  years  ago. 

Wrought  iron — often  called  malleable  iron — is  still  pro- 
duced, although  in  amount  which  is  relatively  small,  by 
methods  which  have  the  attractive  title  of  direct  processes. 
But  by  far  the  greater  quantity  of  wrought  iron  is  made  by 
the  indirect  method.  In  the  latter-named  method  pig  iron  is 
first  produced,  which  is  afterwards,  by  the  puddling  process, 
converted  into  wrought  iron.  Pig  iron  is  the  chief  product  of 
the  blast  furnace  •  in  it  is  concentrated  more  than  90  per  cent, 
of  iron — even  if  the  ore  from  which  it  was  extracted  con- 
tained only  33  per  cent,  of  that  metal.  It  is  the  business 
of  the  puddler  to  purify  the  pig  iron,  and  thereby  change  it 
from  a  somewhat  brittle,  unweldable  mass  into  metal  having 
the  useful  qualities  mentioned  at  the  opening  of  this  chapter. 

Present-day  puddling  is  of  two  kinds — (a)  dry  puddling, 
and  (b)  wet  puddling. 

Wet  Puddling  or  Pig  Boiling. — A  comparison  of  the  per- 
centage composition  of  the  pig  iron  used  and  the  wrought 

*  These  terms  are  explained  in  the  previous  chapter. 


12 


IRON    AND    STEEL    MANUFACTURE. 


iron  produced  may  convey  an  idea  of  the  work  to  be  done  by 
the  puddler : — 


Constituents 

Chemical 
Symbols. 

Forge 
Pig  Iron. 

Wrought  Iron 
Produced. 

Graphitic  carbon,    .         .        .    ( 
Combined  carbon,   . 

c 
c 

2-0 
1-5 

6-05 

Total  carbon, 

c 

Si 

3-5 
1*3 

0-05 
0'20 

Phosphorus,     .... 

Sulphur,  .  '<    >$  "  '  Y*  i    '  !. 
Manganese,      .   "     .        .         . 
Cinder  or  slag, 
Iron  (by  difference),         . 

P 

s 

Mn 
Fe 

1-3 

o-i 

0-5 
none 

A 

0-15 
0-03 

o-oi 

2-80 
A 

100-0 

100-00 

Graphitic  Carbon  is  not  in  chemical  combination.  From 
rich,  grey  pig  iron  it  is  sometimes  possible  to  detach  flakes  of 
graphite  (which,  chemically,  is  carbon)  from  a  fractured  part. 
Combined  carbon  cannot  be  separated  in  this  manner. 

These  figures  show  that  the  impurities  in  the  pig  iron  are 
largely,  indeed  in  some  instances  almost  entirely,  removed 
during  puddling.  The  removal  is  effected  by  burning  out  the 
impurities,  or,  to  express  the  idea  more  scientifically,  the 
impurities  are  removed  by  oxidation.  Fortunately,  the 
oxidising  action  is  selective;  the  impurities  which  we  wish  to 
eliminate*  are,  under  the  conditions  set  up  by  the  puddler, 
more  readily  oxidised  than  the  iron,  and  they  therefore 
become  separated  from  the  iron. 

Briefly  put,  the  puddling  process  consists  in  melting  suitable 
pig  ironf  in  a  properly-prepared  puddling  furnace,  and  stirring 
and  rubbing  it,  or,  to  use  the  trade  term,  "  rabbling"  it,  so  as 
to  bring  the  melted  pig  iron  into  intimate  contact  with  the 
oxides  (chiefly  oxides  of  iron)  which  constitute  the  "fettling" 
— including  the  fluxing  oxide — in  the  furnace.  The  carbon, 

*This  long  word  is  from  the  Latin,  and,  in  plain  English,  means  "to 
thrust  out  of  doors. " 

tit  is  one  of  the  merits  of  the  puddling  process  that  a  great  range, 
or  variety,  of  pig  iron  can  be  successfully  dealt  with  during  the 
process. 


THE    PUDDLING    PROCESS.  13 

silicon,  manganese,  phosphorus,  and  sulphur  are,  as  previously 
stated,  attacked  by  oxygen  and  almost  completely  removed 
from  the  pig  iron.  The  products  resulting  from  the  oxidation 
of  the  carbon,  being  gaseous,  escape  by  the  chimney;  the 
other  oxidised  products  enter  into  the  slag. 

It  may  be  accepted  as  one  of  the  fundamental  principles  in 
metallurgy  that  when  an  element — such  as  carbon,  silicon, 
sulphur,  or  phosphorus — existing  in  chemical  union  with  a 
metal,  combines  chemically  with  oxygen,  the  resulting  oxidised 
product  must,  when  melted,  separate  itself  from  the  remaining 
metallic  portion.  Metals  which  become  oxidised  are  subject 
to  the  same  general  law.  To  this  principle,  or  law,  there  are 
a  few  well-known  and  easily  explained  exceptions. 

And  if  oxidised  metal  parts  with  its  oxygen — becomes 
deoxidised,  or  reduced  to  the  metallic  state  —  the  newly 
liberated  portion  joins  the  metal  in  the  furnace. 

These  are  important  points.  If,  for  instance,  a  pig  iron 
contains  1  per  cent,  of  silicon,  it  is  clear  that  there  must  be 

1  per  cent,  less  iron  in  the  pig  iron,  and  it  might  be  inferred 
that,  provided  the  other  impurities  are  the  same  in  amount  in 
each  case,  the  yield  of  wrought  iron  from  a  pig  iron  containing 

2  per  cent,  of  silicon  must  be  less  than  the  yield  from  a  pig 
iron    with    only    1    per   cent,    of   silicon.      That  is  not  so, 
however.     One  ton  of  pig  iron  containing  1J(=  1 '2 5)  per 
cent,  of  silicon  is  theoretically  capable  of  liberating  nearly  1 
cwt.  of  iron  from  the  ferrous  oxide  in  the  fettling,  or  the 
cinder,  in  the  furnace,  and  pig  iron  with  double  that  per- 
centage of  silicon  is  capable  of  liberating  2  cwts.  of  iron.    The 
theoretical  increase  in   yield   is  never  attained  in  practice. 
But  if  the  greater   part   of  the   oxygen   for  purifying  the 
pig  iron  is  obtained  from  metallic   oxides,  such  as  in  the 
fettling  and  the  cinder,  the  weight  of  wrought  iron  produced 
will   be   considerably  greater  than    the  weight  of  pig  iron 
charged. 

The  silic^,  (Si02)  formed  by  the  oxidation  of  silicon  (Si) 
unites  with  iron  oxide  (FeO)  and  together  they  go  into  the 
slag.  Certain  pig  irons  are  known  as  "  hungry  pigs,"  because 
they  "eat"  so  much  of  the  fettling.  The  yield  from  such 


14 


IRON   AND    STEEL   MANUFACTURE. 


pig  iron  is  great,  the  consumption  of  fettling  is  great,  and  the 
labour  is  severe. 

The  oxidation  of  carbon  and  of  phosphorus  by  oxide  of  iron 
also  leads  to  increased  yield. 

The  Puddling  Furnace  is  an  oblong  structure  of  firebrick 
strengthened  by  cast-iron  plates,  and  tied  by  iron  rods  which 
extend  along  and  across  the  furnace,  and  are  fastened  by  large 
nuts  at  each  end.  Each  plate  is  thus  tightly  braced  against 


Fig.  1. — General  View  of  Puddling  Furnace. 

the  brickwork.  The  furnace  is  of  the  type  which  is  known 
as  reverberatory — that  is,  one  in  which  the  fuel  is  burned  in 
the  fire-grate  at  one  end  and  the  flame  from  which  is  drawn 
towards  the  chimney  at  the  other  end.  The  under  surface  of 
the  brick  roof — which  is  a  slanting  one — is  thus  heated,  and 
it  is  chiefly  the  heat  which  is  reflected  from  the  roof,  or,  as 
the  word  reverberatory  means,  is  beat,  back,  which  causes 
the  high  temperature  in  the  working  part  of  the  furnace. 
The  fuel  does  not  come  into  contact  with  the  "metal"  in 


THE    PUDDLING   PROCESS. 


15 


the   furnace  —  an  arrangement   which    leads   to   substantial 
advantages. 


«     n 


CO  F      G     H 

/    /   /•••/  I.  / 


Fig.  2.— Vertical  Longitudinal  Section  of  Puddling  Furnace 


A,  Damper.          B,   Stack. 

C,  Nut  at  end  of  tie-rod. 

D,  Flue-bridge.    E,    Plates. 

F,  Working  door. 

G,  Fettling. 


H,  Reverberatory  roof. 

J,    Fire-bridge.        K,  Staff-hole. 

L,   Coal-firing  opening. 

M,  Grate-bars. 

N,  Buckstave.         0,  Ashpit    ^ 


Fig.  3.— Plan  of  Puddling  Furnace. 

A,  Flue.  B,  Forehearth.     I         D,  Iron  plating. 

C,  Working  part.  E,  Ashpit. 

At  a  convenient  height  above  the  ground  level  the  iron 
castings  which  support  the  fettling  of  the  working  bed  of  the 


16 


IRON    AND    STEEL    MANUFACTURE. 


furnace  are  so  laid  that  air  can  circulate  freely  underneath  to 
keep  the  iron- work  cool.  Separating  the  fire-grate  from  the 
working  bed  is  the  fire-bridge — a  hollow  iron  casting  under 
which  air  can  be  caused  to  pass.  At  the  other  end  of  the 
working  bed  is  the  fine -bridge,  which  is  of  similar  design. 
The  flue,  which  is  a  sloping  passage,  connects  with  the 
chimney,  or  stack,  as  it  is  often  called.  The  chimney,  which 
is  sometimes  50  feet  high,  is  built  of  bricks  braced  by  angle 


Fig.  4. — Puddling  Furnace — 
Cross  -  section  through 
Grate. 


Fig.  5. — Puddling  Furnace— 
Cross-section  between  Fire- 
bridge and  Flue-bridge. 


irons  up  the  corners :  these  are  bound  to  each  other  by  tie- 
rods  and  nuts.  It  is  surmounted  by  a  damper  which  is 
hinged  and  controlled  by  means  of  a  chain,  the  lower  end 
of  which  can  be  easily  reached. 

Instead  ot  a  heavy  brick  stack  for  each  furnace  it  is  now 
not  unusual  to  arrange  for  four  puddling  furnaces  to  be 
worked  by  one  stack  consisting  of  a  tall  cylindrical  steel 
casing  lined  with  suitable  bricks. 


THE    PUDDLING    PROCESS.  17 

As  a  high  temperature  is  required  in  the  puddling  furnace 
the  area  of  the  fire-grate  is  larger  in  proportion  to  the 
working  part  than  is  usual  in  reverberatory  furnaces.  The 
area  of  the  grate  is  generally  more  than  one-third  the  area  of 
the  working  part.  The  grate-bars  are  of  wrought  iron,  and 
are  supported  on  iron  bearers.  The  bars  are  rolled  in  long 
lengths  of  suitable  section,  and  are  cut  into  shorter  pieces  to 
fit  the  grate.  They  can  be  readily  removed  when  required. 
An  injector — a  pipe  with  a  widened  end  into  which  a  jet  of 
steam  is  injected — may  be  provided.  The  force  of  the  steam 
induces  air  to  enter  the  pipe,  through  which  it  is  conveyed 
to  the  furnace. 

In  front  of  the  furnace  are  four  openings  known  respectively 
as  the  firing-hole,  the  staff-hole,  the  door,  and  the  cinder-notch 
or  cinder-hole.  These  are  all  shown  on  figs.  1  and  2. 

Through  the  firing-hole  fuel  is  fed  to  the  fire-grate.  It  is 
customary  to  partly  close  it  by  placing  lumps,  and  some  small 
pieces,  of  coal  on  the  sill.  A  useful  purpose  is  served  by  the 
gases  from  the  gentle  distillation  of  this  coal.  These  gases 
are  drawn  into  the  furnace. 

The  largest  opening — the  one  for  the  door — has  a  heavy 
iron  projecting  sill,  called  the  foreplate.  The  working  door 
consists  of  large  firebricks  or  slabs  set  in  an  iron  frame 
suspended  from  one  end  of  a  lever.  It  is  raised  when 
required  by  pulling  down  the  other  end  of  the  lever  by 
means  of  a  chain.  When  the  chain  is  released  the  door 
slides  down  and  closes  the  opening.  At  the  centre  of  the 
lower  part  of  the  door  is  a  small  opening  known  as  the 
stopper  hole  or  stopper  notch.  Under  the  foreplate  is  the 
cinder-hole,  and  through  it  the  cinder  or  slag  is  tapped  off. 

The  surface  of  the  fire-bridge  and  flue-bridge,  and  the 
plates  which  support  the  working  bottom,  are  all  carefully 
covered  with  firebrick,  or  with  fettling,  where  they  would  be 
otherwise  exposed  to  the  heat  of  the  furnace. 

The  chief  materials  used  for  fettling  are  : — 

Best  Tap,  the  cinder  or  slag  from  reheating  furnaces  which 
are  worked  with  (basic)  cinder  bottoms ; 

Bull-dog,  puddler's  cinder  or  slag  which  has  undergone 
roasting  to  render  it  less  fusible  (not  so  easily  melted) ; 

Purple  Ore,  the  rich  residue  of  ferric  oxide  (with  about 

2 


18 


IRON    AND    STEEL    MANUFACTURE 


4  per  cent,  of  other  compounds)  left  after  the  treatment  of 
iron  and  copper  pyrites ; 

Hematite  Ore,  a  rich  hematite  ore  mined  in  the  North-west 
of  England ;  * 

Pottery  Mine,  f  an  iron  ore  mined  in  the  pottery  district  of 
North  Staffordshire. 


AVERAGE  COMPOSITION  OF  FETTLING  MATERIALS. 


Constituents. 

Chemical 
.  Formulae. 

Best  Tap. 

Bull  Dog. 

"'") 
Purple  Ore 
(Dried). 

Ferrous  oxide, 

FeO 

68-1 

3-8 

Ferric  oxide,   . 

Fe203 

26-5 

69-6 

96-0 

Manganous  oxide,    . 

MnO 

1-2 

0-7 

... 

Silica,      . 

Si02 

2-9 

24-3 

2-0 

Phosphoric  acid  , 

Po05 

0-9 

0-8 

Sulphur,  . 
Lime, 

Magnesia, 

S 
CaO 
MgO 

0:3 
0-1 

I    o-s: 

Other 
constituents 
in  small 
quantities. 

100-0 

100-0 

lOO'O 

Metallic  iron,  . 

Fe 

71-52 

51-68 

07-20 

Preparation  of  the  Puddling  Furnace  for  Work — On  the 
top  of  the  iron  bed-plates  little  lumps  of  "  best  tap "  are 
charged  so  as  to  form  a  coating  about  3  inches  thick. 
The  temperature  of  the  furnace  is  then  raised  to  such  a  pitch 
that  the  best  tap  begins  to  soften.  The  coating  is  covered 
over  with  a  layer,  about  2  inches  thick,  of  scale  or  other 
fettling,  such  as  ground  bull  dog,  purple  ore,  or  hematite  ore. 
These  are  varied  to  suit  the  class  of  pig  iron  which  is  used, 
and  the  quality  or  the  purpose  for  which  the  wrought  iron  is 
to  be  produced.  The  purer  the  pig  iron  the  more  fusible 
must  the  fettling  be :  the  less  pure  or  more  "  hungry  "  the 
pig-iron  the  less  fusible  must  be  the  fettling.  The  sides  are 
also  well  fettled,  the  fettling  being  firmly  rammed  into  the 
recesses  formed  by  the  firebricks  which  project  over  the  fire- 
and  flue-bridges.  A  light  charge  of  scrap  iron  is  then  charged, 

*  See  analysis  on  p.  178.  f  See  analysis  on  p.  242.    -  ^ 

JBy  difference. 


THE    PUDDLING   PROCESS.  19 

raised  to  a  welding  heat,  oxidised,  and  rolled  over  the  fettling 
so  as  to  glaze  it  with  rich  oxide  of  iron. 

The  Puddling  Process. — The  furnace,  when  fettled  and  hot, 
is  ready  for  charging.  Through  the  open  door  about  f  cwt. 
of  hammer  slag,  or  other  fusible  iron  oxide,  and  4^  or  5 
cwts.  of  pig  iron  are  thrown  as  shown  in  fig.  6.  The  door 
is  then  lowered,  a  small  iron  plate  is  set  in  front  of  the 


Pig.  6. — Charging  a  Puddling  Furnace. 

stopper  hole,  and  a  little  quantity  of  fine  ore  is  placed  on 
the  foreplate  so  as  to  prevent  access  of  air  through  any  worn- 
out  parts. 

The  puddling  process  may  conveniently  be  described  as 
divided  into  four  stages.  The  first  stage  merges  quietly'  into 
the  second  stage,  which  in  its  turn  glides  into  the  succeeding 
one. 

The  First  or  Melting-down  Stage.— In  the  course  of  about 


20  IRON   AND   STEEL    MANUFACTURE. 

20  minutes  after  charging,  the  exposed  parts  of  the  pig  iron 
will  have  become  red  hot.  The  "pigs"  are  then  turned  over  so 
as  to  be  heated  more  uniformly.  Melting  begins  soon  after,  and 
the  melted  portions  drip  and  flow  into  the  lowest  part  of  the 
working  bed,  where  it  is  well  stirred.  The  tools  for  turning 
over  the  pig  iron  and  for  stirring  the  melted  materials  are 
inserted  through  the  stopper  notch. 

During  the  melting  down  much  silicon  and  manganese  are 


Fig.  7. — Pig  Iron  in  Puddling  Furnace. 

oxidised,  and  a  considerable  quantity  of  phosphorus  is  also 
oxidised  All  the  oxidised  products  leave  the  pig  iron  and 
combine  with  some  of  the  melted  fettling  to  form  the  slag  or 
cinder.  This  stage  occupies  about  30  minutes  in  all. 

The  Second  or  Clearing  Stage  occupies  about  10  minutes. 
In  it  the  remainder  of  the  silicon  and  manganese  and  a 
further  quantity  of  the  phosphorus  are  oxidised  and  removed 


THE    PUDDLING    PROCESS. 


from  the  pig  iron.  A  high  temperature  is  maintained,  and 
the  charge  is  vigorously  rabbled  (that  is,  stirred  or  worked 
with  an  iron  tool  called  a  rabble),  so  as  to  promote  a  more 
rapid  and  intimate  contact  between  the  pig  iron  and  the  slag 
and  fettling;  thus  hastening  the  oxidation  of  the  impurities 
in  the  pig  iron  by  the  oxides  in  the  fettling  and  the  fluxes, 
and  by  the  air  which  is  passing  through  the  furnace. 


Fig.  8.—  Puddler  Rabbling  a  Charge. 

In  the  Third  or  Boiling  Stage,  which  occupies  about  30 
minutes,  nearly  all  the  carbon  is  removed  and  most  of  the 
remaining  phosphorus  is  eliminated.  The  temperature  is 
regulated  as  required,  and  the  charge  is  still  vigorously 
rabbled.  As  the  carbon  at  this  stage  is  oxidised  and  forms 
carbon  monoxide  (CO),  which  is  a  gas,  the  efforts  of  the  gas 
to  reach  the  surface  of  the  now  somewhat  pasty  mass  cause 
repeated  risings  and  subsidings  and  an  appearance  suggestive 
of  boiling.  When  the  bubbles  of  carbon  monoxide  reach  the 


22  IRON    AND   STEEL    MANUFACTURE. 

surface,  they  are  met  by  a  current  of  air  which  oxidises  the 
carbon  monoxide  (CO)  into  carbon  dioxide  (C02).  The  blue 
flames  seen  at  the  surface  of  the  bath  of  metal  and  slag,  when 
the  burning  of  the  monoxide  takes  place,  are  known  as 
"puddlers'  candles."  The  charge  swells  considerably,  and 
"boilings" — the  most  frothy  part  of  the  cinder — are  tapped 
off.  It  is  at  this  stage  that  the  metal  "comes  to  nature." 
Bright  specks  of  metal  appear,  and  become  more  numerous 
and  larger. 


Pig.  9. — Drawing  Puddled  Ball  from  Furnace. 

The  Last  or  Balling  Stage  occupies  about  20  minutes. 
It  is  the  heavy  duty  of  the  puddler  to  gather  together  the 
metal,  with  only  a  little  slag,  into  balls  of  convenient  size. 
He,  therefore,  raises  the  metal,  which  is  now  in  a  spongy 
condition,  and  divides  it  into  pieces  of  about  75  to  100  pounds 
each.  He  then  rolls  each  piece  into  a  ball,  and  as  each 
puddled  ball  is  finished  it  is  kept  away  from  oxidising 
influences  as  much  as  possible,  and,  while  as  hot  as  the 
furnace  can  be  kept,  is  withdrawn  by  means  of  tongs  over 


THE    PUDDLING    PROCESS.  23 

the  foreplate,  and  is  usually  dropped  on  to  an  iron  trolley 
which  is  ready  to  receive  it.  If,  however,  the  furnace  is  not 
far  from  the  site  of  the  next  operation  no  trolley  is  used,  but 
the  hot  puddled  ball  is  bodily  dragged  across  the  well-swept 
"race" — the  iron  plates  which  constitute  part  of  the  flooring 
The  puddled  balls  are  quickly  conveyed  to  the  shingler,  whose 
business  it  is  to  shingle  the  ball  either  by  squeezing  or 
hammering.  The  appliances  for  shingling  are  described  on 
pp.  29  and  30. 

During  shingling  there  is  a  copious  flow  of  cinder  from  the 
mass.  The  compressing  of  a  porous  lump  of  metal  (such  as  a 
puddled  ball)  causes  a  great  rise  in  the  temperature  of  th<? 
mass.  This  favours  expulsion  of  the  slag,  but  the  expulsion 
is  never  complete.  If  the  puddled  ball  is  shingled  by  a 
hammering  action,  the  shingler  turns  over  the  mass  from  time 
to  time  between  the  strokes.  Sometimes  an  additional  ball, 
or  balls,  are  welded  together  during  shingling.  This  operation 
is  known  as  "  doubling."  When  the  mass  has  been  sufficiently 
worked  and  shaped  into  a  somewhat  rough,  oblong  block,  it  is 
taken  to  the  forge  rolls,  where  it  is  rolled  into  a  puddled  bar. 

The  further  treatment  of  the  puddled  bar  is  described  on 
p.  28,  and  the  forge  rolls  (or  forge  train)  on  p.  32. 

The  foregoing-is  but  a  brief  and  bare  outline  of  a  process 
which  is  most  interesting  to  watch.  The  procedure  varies 
somewhat  according  to  the  pig  iron  provided,  and  the  whole 
operation  is  one  which  calls  for  strength  of  arm  and  soundness 
of  judgment. 

The  furnace  requires  to  be  fettled  before  each  charge,  but 
especially  at  the  commencement  of  each  shift.  Slag  is  tapped 
off,  when  required,  into  a  suitable  little  truck — the  cinder 
truck — as  shown  in  fig.  10.  The  waggon  is  also  shown,  full 
of  cinder,  in  the  foreground  of  fig.  1. 

A  puddler  and  his  underhand  between  them  work  through 
six  heats  of  about  5  cwts.  each  in  the  course  of  a  working 
day,  with  a  yield  of  about  30  cwts.  of  puddled  balls. 

The  fuel  used  is  a  bituminous  coal  (see  analysis  on  p.  226), 
which  yields  a  long  flame.  About  24  cwts.  are  required  for 
each  ton  of  puddled  balls  produced. 


24  IRON    AND    STEEL    MANUFACTURE. 

In  many,  probably  most,  instances  the  weight  of  puddled 
balls  produced  is  about  equal  to  the  weight  of  pig  iron 
charged,  but  there  is  often  a  notable  increase  of  iron, 
especially  when  the  pig  iron  and  the  fettling  are  judiciously 
selected  so  as  to  suit  each  other.  It  is  clear  that  the  in- 
crease of  iron  is  derived  from  the  iron  oxides  with  which 
the  furnace  is  liberally  fettled,  and  especially  from  that 
which  the  puddler  looks  on  as  a  flux — namely,  from  the 


Fig.  10.— Tapping  Cinder  from  Puddling  Furnace. 

hammer  scale  or  other  iron  oxides  which  are  thrown  into  the 
furnace  before  charging  the  pig  iron.  And  it  is  also  clear 
from  the  composition  of  tap  cinder,  and  the  quantity  sold, 
that  the  ferric  oxide  (Fe203)  which  predominates  in  much  of 
the  fettling  material  must,  during  the  puddling  process,  have 
been  reduced  to  magnetic  oxide ;  the  liberated  oxygen  doing 
useful  work  in  oxidising  the  metalloids,  as  substances  such  as 
silicon,  phosphorus,  &c.,  are  called.  The  composition  of 


THE    PUDDLING    PROCESS. 


25 


magnetic  oxide  is  Fe304,  which  is  sometimes  looked  on  as 
Fe203,  FeO.  Adopting  the  formula  introduced,  for  convenience 
of  comparison,  on  p.  5,  ferric  oxide  may  be  regarded,  for 
purposes  of  comparison,  as  Fe609.  This,  on  giving  up  oxygen, 
is  reduced  to  magnetic  oxide,  which  may  be  noted  as  Fe608. 

There  is  good  reason  for  believing  that  some  part  of  the 
fettling,  or  the  flux,  acts  as  an  oxygen  carrier — the  lower  iron 
oxide  becoming  highly  oxidised  (peroxidised)  by  the  oxygen 
of  the  air  passing  through  the  furnace,  and  readily  giving  np 
the  newly -acquired  oxygen.  See  chemical  equations  on 
pp.  '21  and  28. 

AVERAGE  COMPOSITION  OF  SLAGS  OR  CINDERS  FROM  THE 
PUDDLING  PROCESS. 


Constituents. 

Chemical 
Formula;.. 

Average 
Tap  Cinder. 

Boilings. 

Hammer 

Slay. 

Ferrous  oxide, 

FeO 

61-5 

62-7 

54-6 

Ferric  oxide,   . 

Fe203 

8-3 

7-1 

19-5 

Manganous  oxide, 

MnO 

2  "2 

2-6 

2-1 

Silica, 

SiO. 

20-3 

20-9 

17-5 

Phosphoric  acid, 

PA 

5-3 

6-2 

5-1 

Sulphur,  . 

S 

0-7 

} 

Lime, 

CaO 

1-5 

1-5* 

1-4* 

Magnesia, 

MgO 

0-2 

I 

100-0 

100-0 

100-0 

Metallic  iron,  . 

Fe 

53-64 

53-74 

56-12 

THEORETICAL  CONSIDERATIONS. 

Of  the  elements  eliminated  during  puddling  the  only  one 
to  become  gasified  is  carbon,  which,  combining  with  oxygen, 
forms  carbon  dioxide  (C02),  and  escapes  by  the  stack  into  the 
air.  All  the  other  elements,  when  oxidised,  go  into  the 
cinder.  The  cinder  must  be  of  such  a  composition  that  it 
will  become,  and  remain,  fluid,  or  at  least  semi-fluid,  during 
the  operation.  One  of  the  first  elements  to  be  eliminated  is 
silicon  (Si),  which  is  easily  oxidised  and  forms  silica  f  (Si02). 


*Bv  difference. 


t  White  sand  is  almost  pure  silica. 


26  IRON    AND    STEEL    MANUFACTURE. 

Now,  silica  is  prone  to  unite  with  oxide  of  iron  (FeO).  The 
union,  or  chemical  combination,  of  the  two  results  in  the 
formation  of  ferrous  silicate  (2FeO  .  Si02) ;  a  compound  which 
fuses,  or  melts,  with  comparative  ease.  Hence  some  of  the 
fettling  or  cinder  must  contain  excess  of  ferrous  oxide  in 
order  that  free  silica  may  not  interfere  with  the  process.  The 
quaint  idea  of  the  late  W.  Mattieu  Williams,  that  the  fluid 
cinder  may  be  compared  to  soap  suds,  and  assists  in  the 
cleansing  of  the  pig  iron,  is  not  far-fetched. 

Into  the  intricacies  of  acids  and  bases  the  size  and  scope  ot 
this  book  forbids  entrance,  but  it  may  convey  sufficiently 
clear  ideas  at  this  point  to  say  that  the  bases  commonly  met 
with  in  metallurgy  can  enter  into  chemical  union  with  the 
metallurgical  acids,  and  that  the  resulting  compound  has  a 
much  lower  melting  point  than  either  the  acid  alone  or  the 
base  alone.  The  union  of  the  acid  silica  (Si02)  with  the 
basic  ferrous  oxide  (FeO)  is  a  case  in  point. 

The  following  are  classed  as  acids  by  metallurgists : — 

Phosphoric  acid  or  phosphoric  anhydride,  (I^s) 

Titanic  oxide, (Ti09) 

Silica,     .                           .                           .  (Si02) 
Carbonic    acid     (carbonic     anhydride    or 

carbon  dioxide),        .         .         •         .  (C02) 

The  chief  bases  which  are  of  interest  to  the  iron  and  steel 
metallurgist  are — 

Ferrous  oxide, (FeO) 

Manganous  oxide,    .....  (MnO) 

Lime, (CaO) 

Magnesia, ,*.  (MgO) 

Alumina  (A1203)  may  act  either  as  an  acid  or  a  base, 
according  to  circumstances. 

The  method  by  which  phosphorus  is  eliminated  during 
puddling  was  discovered  by  Geo.  J.  Snelus  in  1872,  and  his 
theory  is  now  universally  accepted.  It  is  this  :  The  phosphorus 
(P2)  is  oxidised  to  phosphoric  acid  (P206),  which  enters  into 


THE    PUDDLING    PROCESS.  27 

chemical  union  with  the   basic  ferrous  oxide  (FeO)   in  the 
cinder,  and  is  held  there. 

Dephosphorisation,  or  the  elimination  of  phosphorus,  cannot 
be  successfully  conducted  unless  under  oxidising  conditions, 
and  in  presence  of  plenty  of  hot  material  of  a  basic  nature. 
The  manganese  (Mn)  which  is  oxidised  becomes  converted 
into  manganous  oxide  (MnO),  which  increases  the  .basic  nature 
of  the  slag.  The  sulphur  which  becomes  oxidised  may 
escape  in  the  gases  or  be  caught  in  the 


The  functions  of  the  fettling  and  cinder  are  h've-fold. 

(a)  To  protect  the  iron  plates  and  other   castings  at  the 
working  bed. 

(b)  To  supply  oxygen  for  removal  of  the  impurities. 

(c)  To  bind  the  grains  together  and  to  prevent  the  oxida- 
tion of  the  surface  of  the  grains — "  to  nourish  the  iron." 

(d)  To    provide    a    base    for    the    phosphorus    and    other 
impurities. 

(e)  To  increase  the  output. 

The    chief   chemical    reactions    which    take    place    during 
puddling  are — 

OXIDATION  BY  ATMOSPHERIC  OXYGEN. 

C  +  02  C02 

Carbon  and        oxygen        yield          carbon  dioxide. 

Si  +  02  Si02 

Silicon  and        oxygen        yield  silica. 

2Mn  +  02  2MnO 

Manganese        and        oxygen        yield      oxide  of  manganese. 

4P  +  502  2P2O5 

Phosphorus        and        oxygen        yield        phosphoric  acid. 

The  phosphoric  acid  unites  with  the  (basic)  ferrous  oxide  in 
the  cinder  or  slag. 

OXIDATION  BY  FERRIC  OXIDE,  WITH  PRODUCTION  OF  MAGNETIC  OXIDE. 

C  +         3Fe,03  CO  +  2Fe3O4 

Carbon      and  ferric  oxide  yield  carbon  monoxide  and  magnetic  oxide. 


28  IRON    AND    STEEL    MANUFACTURE. 

Si  -f         6Fe2O3        =  Si02  +  4Fe804 

Silicon      and  ferric  oxide  yield  silica  and  magnetic  oxide. 

Mn  +         3Fe203  MnO  +  2Fe304 

Manganese  and  ferric  oxide  yield  manganous  oxide  and  magnetic  oxide. 

2P  +        15Fe203       =  P205  +          10Fe304 

Phosphorus  and  ferric  oxide  yield  phosphoric  acid  and  magnetic  oxide. 

Other  chemical  reactions  also  take  place. 

Treatment  of  Puddled  Bars. — The  puddled  bar*  formed, 
as  described  in  previous  pages,  by  rolling  the  hammered  or 
squeezed  puddled  ball,  is  rough  on  the  surface  and  ragged  at 
the  edges.  The  slag  which  it  contains  is  in  splatches  and  not 
well  distributed  throughout  the  bar.  To  remedy  these  defects 
and  to  produce  a  bar  more  uniform  in  composition,  with  less 
slag,  and  the  remaining  slag  more  evenly  distributed — in  fact, 
of  a  quality  sufficiently  good  for  smiths  and  engineers — the 
puddled  bars  are  cut  into  short  lengths,  made  into  oblong 
piles,  reheated  to  a  welding  pitch  in  a  reheating  or  mill  fur- 
nace, and  rolled  out  to  a  finished  section  in  a  set  of  rolls 
known  as  the  "  mill  train  "  into  "  merchant  bar." 

Piles  for  reheating  are  built  up  on  puddled  bars,  or 
merchant  bar,  or  old  wrought  iron,  and  the  pile  is 
arranged  with  due  regard  to  the  intended  shape  of  the 
finished  material. 

Scrap  wrought  iron  is  piled,  brought  to  a  welding  heat 
in  a  ball  furnace  or  scrap  furnace,  and  hammered  into  a 
half -finished  mass  called  a  bloom.  The  bloom  is  reheated 
in  a  mill  furnace  and  rolled  in  the  mill  train  into  finished 


Best  best  and  treble  best  iron  is  specially  made  from  care- 
fully selected  materials  which  are  puddled,  shingled,  rolled, 
cut,  piled,  reheated,  and  rerolled.  The  products  are  systemati- 
cally tested,  and  the  iron  is  of  superior  quality. 

FORGE  PLANT. 

For  consolidating  puddled  balls  and  expelling  slag  squeezers 
are  sometimes  employed.  Of  these,  the  crocodile  squeezer 

*  Known  in  America  as  "  muck  bar." 


THE    PUDDLING    PROCESS.  29 

may  be  taken  as  an  example.  There  are  other  appliances, 
but  squeezing  is  a  system  which  does  not  appear  to  be  in 
favour. 

A  primitive,  but  effective,  appliance  for  shingling  the 
puddled  ball  is  the  helve  (fig.  11),  which  has  a  heavy  iron 
beam  carrying  a  hammer  head  which  can  be  easily  replaced. 
The  beam  rests  on  a  fulcrum  at  one  end,  and  the  other  end  is 
lifted  by  projections  (cams)  on  a  rotating  cylinder.  When 
the  nose  of  the  beam  has  been  raised  to  the  highest  point  to 
which  a  projection  can  carry  it,  the  beam  and  hammer  head 


Fig.  11.— Helve. 

A,  Flywheel.  C,    Hammer  head 

B,  Cam.  D,  Anvil. 

fall  heavily  on  the  puddled  ball  which  has  been  placed  on  the 
anvil  block.  The  next  projection  on  the  revolving  cylinder 
quickly  raises  the  beam  and  hammer  head,  and  again  a  heavy 
blow  is  dealt  when  the  hammer  head  falls  on  the  puddled 
ball.  The  nose  may  be  raised  about  20  inches,  and  about  60 
blows  per  minute  are  delivered.  The  shingler  keeps  turning 
over  the  puddled  ball  between  the  strokes.  To  stop  the 
working  of  the  helve  a  prop  or  sprag  is  inserted,  which  keeps 
the  nose  of  the  beam  above  the  action  of  the  arms  or  pro- 
jections. When  a  fresh  ball  has  been  placed  on  the  anvil 
block,  a  piece  of  iron  is  laid  on  the  upcoming  arm.  This 
causes  the  nose  to  be  lifted  higher ;  the  prop  is  withdrawn, 
thereby  allowing  the  helve  to  resume  work. 


30 


IRON    AND    STEEL    MANUFACTURE. 


The  Steam  Hammer  (fig.  12)  consists  essentially  of  an 
upright  stem  or  frame  supporting  a  vertical  steam  cylinder,  in 
which  works  a  piston  having  a  long  rod  with  a  hammer  head 


Fig.  12.— Steam  Hammer. 


THE    PUDDLING    PROCESS. 


31 


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i^ 

*  isn 

o        ^  « 

j^    H  fa  O  B 


bo 
g      ti) 


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32 


IRON     AND    STEEL    MANUFACTURE. 


or  tup  at  its  lower  end.  By  means  of  'a  lever  controlling  the 
admission  of  steam  to  the  upper  or  the  lower  part  of  the 
cylinder,  the  rate  and  force  of  the  blows  can  be  easily  regu- 
lated. An  anvil  block  is  set  immediately  below  the  tup. 
Both  block  and  tup  can  be  readily  replaced  when  required. 

The  Forge  Train,  in  which  the  shingled  blooms  from  the 
helve  or  hammer  are  rolled  into  puddled  bars,  is  sketched 
in  fig.  13.  This  train  comprises  helical-teeth  pinions  fitted  in 
enclosed  housings,  also  one  pair  of  forge  rolls  with  housings, 
chocks,  brasses,  pins,  boxes,  couplings,  &c.,  and  the  whole 
train  is  mounted  upon  a  massively-designed  girder-section  bed 


Fig.  14. 


plate.  The  advantages  of  this  design  are  that  the  mill  is 
always  kept  perfectly  in  line,  and  the  time  occupied  in 
changing  rolls  is  considerably  reduced. 

Fig.  14  shows  an  end  view  of  the  forge  train. 

Fig.  15  illustrates  a  10-inch  merchant  bar  mill,  or  guide 
mill,  so  called  because  a  set  of  guides  are  provided  for  guiding 
the  oval  section  into  the  finishing  round  groove  of  the  finish- 
ing rolls.  The  merchant  mill  is  designed  for  the  purpose 
of  rolling  wrought  iron  from  a  pile  of  4-inch  puddled  bars 
into  any  desired  section.  The  rolls  shown  are  for  flats,  1J- 
inch  and  If -inch  broad,  of  such  thickness  as  may  be  required. 
For  producing  rounds  or  squares,  the  rolls  for  flats  marked  D 


THE    PUDDLING    PKOCESS. 


33 


would  be  removed  and  a  set  of  rolls  with  oval  and  diamond 
openings  substituted. 


60 

a 

03  'O 

!•§ 

1 


S  ,« 

i  I 

&b  ^'     -5 

S  2     f 


SO  O    tiC^ 

2    W^T! 
(3>iS    9 

'-S  £-3 
f     o  S^ 


34  IRON   AND   STEEL    MANUFACTURE. 

The  mill  comprises  flanged  couplings,  leading  spindle  and 
carriage,  double  helical-teeth  pinions  fitted  into  housings,  with 
a  separate  gland  cover  constituting  an  oil  bath  in  which  the 
pinions  revolve.  The  bolting  rolls  and  strand  rolls  are  fitted 
with  housings,  chocks,  brasses,  and  necessary  wrought-iron 
work,  guides,  guards,  &c.,  and  two  pairs  of  chilled  guide  rolls 
are  provided  for  giving  a  good  finish  to  round  and  square 
bars.  These  guide  rolls  also  are  fitted  with  necessary  housings, 
glands,  stools,  brasses,  wrought-iron  work,  guides,  sfec.,  and  the 
whole  mill  is  mounted  on  a  girder-section  bed-plate.  For  the 
sake  of  clearness,  some  of  the  usual  fittings  have  been  omitted 
from  the  sketch. 

These  mills  are  of  the  type  manufactured  by  Messrs.  Akrill, 
Limited,  West  Bromwich. 

Best  Yorkshire  Iron  is  made  from  special  (cold  blast)  pig 
iron  which  undergoes  a  refining  process  before  being  puddled 
in  small  charges.  Its  manufacture  is  conducted  with  great 
care,  the  puddled  iron  is  conscientiously  examined,  the  blooms, 
&c.,  are  heated  well,  and  a  large  amount  of  work  is  put  upon 
the  iron.  The  qualities  which  have  given  it  a  world- wide 
reputation  are  its  reliability  even  under  most  exacting  condi- 
tions, its  capability  of  standing  repeated  reheatings,  and  its 
power  of  enduring  without  deterioration  much  punishment  in 
the  hands  of  the  smith  and  engineer. 


35 


CHAPTER  IV. 

STEEL:  CRUCIBLE  CAST  STEEL  FOR  TOOLS  AND 
CUTLERY. 

OF  the  services  rendered  to  civilisation  by  the  production  of 
good  tool  steel,  it  would  be  difficult  to  speak  too  highly. 

Steel  is  essentially  a  compound  of  iron  and  carbon.  It 
contains  other  elements,  some  intentionally  added  to  confer 
certain  qualities  on  the  steel ;  others  are  unavoidably  present, 
but  cannot  be  tolerated  in  more  than  small  percentages. 

The  best  quality  steel  for  tools  and  for  cutlery  is  known  as 
crucible  cast  steel.  The  process  is  still  carried  on — chiefly 
in  Sheffield — with  slight  variations  in  the  details  of  the 
system  devised,  after  many  trials,  by  Benjamin  Huntsman 
about  the  year  1740. 

High-class  crucible  cast  steel  is  made  by  the  application  of 
intelligent  experience  to  the  correct  treatment  of  carefully- 
selected  materials  of  high  quality — of  such  experience  as  has 
been  practically  acquired  through  generations  of  skilful 
working. 

Outline  of  the  Process  of  Manufacture. — The  iron  used  is 
brought  from  Sweden,*  where  the  pig  iron  is  smelted  from 
the  purest  ores  by  the  purest  fuel.  The  pig  iron  is  worked 
into  wrought  iron  in  a  type  of  furnace  which  originated  in 
the  north-west  of  England,  and,  being  adapted  to  Swedish 
requirements,  is  named  the  Swedish-Lancashire  hearth,  f 
The  wrought  iron  is  hammered  into  long  flat  bars,  and  these 
bars  are  supplied  to  steel-making  firms.  From  the  bars 
crucible  cast  steel  is  manufactured  in  two  definite  stages. 
Firstly,  the  bars  are  subjected  to  a  cementation  process  by 
being  heated  for  several  days  in  contact  with  charcoal  in 
boxes,  the  tops  of  which  are  cemented  to  exclude  air. 

*  Some  American  steel-makers  believe  that  Swedish  iron  is  not 
necessary.  A  high  degree  of  purity  is  always  required. 

t  The  famous  Dannemora  bar  iron  is  produced  from  pig  iron  by  the 
old  Walloon  fining  method. 


1 


STEEL    FOR   TOOLS    AND    CUTLERY. 


37 


Secondly,  in  order  to  produce  steel  in  masses  which  are  free 
from  slag  arid  of  the  same  composition  and  qualities  through- 
out, the  "cemented  bars"  are  broken,  graded,  melted  in  a 
crucible  at  a  white  heat,  and,  with  proper  precautions,  poured 
into  prepared  moulds  so  as  to  form  ingots  which  can  be 
worked  into  the  shapes  desired. 

The    cementation    furnace   is   externally   a   tall,  tapering 
structure  (the  stack),  which  is  sometimes  square  at  the 


Fig.  17. — Cementation  Furnace — Elevation  and  Section. 


A,  Stack. 

B,  Arch. 

C,  Chimney. 

D,  Manhole. 


E,  Cementation  pots. 

F,  Fire-grate. 

G,  Ashpit. 


and  circular  towards  the  top.  Fig.  16  shows  a  view  of  the 
stacks  of  steel  furnaces  at  Messrs.  Thomas  Firth  &  Sons' 
Norfolk  Works,  Sheffield. 

Inside  the  stack,  at  its  base,  a  fire-grate  extends  from  front 
to  back;  and  alongside  the  fire-grate  two  long  troughs — or 
"  cementation  boxes " — are  placed.  These  are  shown  in 


00  IRON    AND    STEEL    MANUFACTURE. 

section  on  fig.  17,  and  a  plan  is  shown  on  fig.  18.  In  order 
that  the  heat  from  the  fire-grate  may  find  free  and  fairly 
equal  access  to  all  parts  of  the  outside  of  the  cementation 
boxes,  they  are  set  on  bearers,  and  passages  are  arranged 
leading  to  short  chimneys.  Between  the  walls  in  which  the 
short  chimneys  are  set,  a  brick  arch  is  built  at  some  little 
distance  above  the  boxes,  or  "pots,"  as  they  are  sometimes 
called. 

The  inner  walls  and  arch  are  of  good  firebrick ;  the  lower 
part  of  the  stack  is  also  of  good  firebrick,  while  the  upper 
part  may  be  of  more  common  bricks.  The  stack — which  is 


Fig.  18. — Cementation  Furnace— Plan. 
A,  Cementation  pots.     |     B,  Passage  to  flues.      |     C,  Fire-grate. 

generally  about  50  feet  high — prevents  excessive  radiation 
from  the  arch,  and  also  serves  the  usual  purposes  of  a  chimney. 
A  manhole  is  provided  in  the  brickwork,  and  "  trial  holes  " 
are  left  in  the  brickwork,  which  correspond  to  similar  holes  in 
the  ends  of  the  boxes. 

The  Cementation  Boxes,  or  Pots,  are  of  firestone  slabs 
cemented  with  a  mortar  of  good  fireclay.  They  are  from  8  to 
16  feet  in  length,  a  fair  average  size  being  12  feet  long,  4 
feet  deep,  and  4  feet  wide.  The  capacity  of  a  furnace  is  from 
15  to  30  tons.  The  boxes  are  packed  by  placing  in  each  a 
layer  of  selected  hardwood  charcoal,  which  has  been  sifted  to 


STEEL    FOR    TOOLS    AND    CUTLERY.  39 

exclude  pieces  generally  smaller  than  half -inch.  Some  old 
charcoal  is  used  along  with  the  new.  A  layer  of  the  flat 
bars — which  are  frequently  3  inches  broad  by  three-quarters 
of  an  inch  thick — is  placed  on  the  charcoal,  and  completely 
covered  at  sides,  ends,  and  on  top  with  charcoal.  Alternate 
layers  of  flat  bars  and  charcoal  are  packed  in.  the  upper- 
most one  being  of  charcoal.  This  is  covered  with  a  thick 
coating  of  clay  or  of  wheelswarf.  Wheelswarf  is  collected 
from  the  troughs  of  the  Sheffield  grindstones,  and  consists  of 
the  worn-away  material  of  the  grindstones,  mixed  with  the 
steel  dust  which  has  been  ground  away.  The  dust  "  sparks  " 
as  it  is  ground ;  that  is,  it  becomes  oxidised,  so  that  the 
wheelswarf  is  really  a  mixture  containing  iron,  iron  oxide, 
and  silica  from  the  grindstone.  A  coating  of  wheelswarf  is 
sufficiently  porous  to  permit  the  escape  of  air  from  the  pots 
while  the  contents  are  being  heated,  but  which  readily  fuses 
even  at  a  rnoderately-high  temperature,  and  so  forms  an  air- 
tight cover.  Iron  (or  steel)  in  the  wheelswarf  is  incidentally 
oxidised  during  the  rise  of  temperature,  and  iron  oxide  and 
silica,  when  heated,  easily  fuse,  as  mentioned  in  the  paragraph 
on  welding  and  the  chapter  on  puddling. 

When  the  pots  are  packed  and  duly  covered,  the  front  of 
the  furnace  is  bricked  up,  and  a  fire  is  kindled  in  the  grate. 
The  long  grate  of  the  furnace  is  fed  from  both  ends;  a  free- 
burning  coal  which  does  not  "clinker  being  used.  A 
non-clinkering  coal  is  one  which  leaves  a  white  ash  in  fine 
powder.  In  the  course  of  24  hours  or  so  a  red  heat  is 
attained,  and  the  full  heat,  a  bright  orange  (about  2,120°  R, 
or  1,160°  C.),  is  reached  in  about  48  hours.  The  full  heat 
may  be  maintained  for  a  week  or  more,  according  to  the 
degree  of  carburisation,  or  "temper,"  aimed  at.  The  chief 
effect  of  this  treatment  is  the  penetration  of  carbon  into  the  solid 
iron  bars. 

While  packing  a  box,  a  few  "  tap  bars,"  or  "  trial  bars,"  are 
set  with  their  ends  protruding  through  the  slot  left  in  one  end 
of  the  box.  When  there  is  reason  to  believe  that  the  correct 
carbonisation  (or  conversion)  has  been  arrived  at,  one  of  the 
tap  bars  is  withdrawn,  and  the  vacated  space  in  the  end  slab 
of  the  box  is  carefully  filled  with  white  coal  ash  or  other 
suitable  material.  The  tap  bar,  when  cold,  is  broken,  and  the 


40  IRON    AND    STEEL   MANUFACTURE. 

fracture  is  examined.  The  experienced  eye  can  judge  such 
fractures  with  great  accuracy.  When  conversion  is  thus 
judged  to  have  gone  far  enough— allowance  being  made  for 
further  carburisation  during  part  of  the  time  of  cooling — the 
firing,  or  stoking,  is  stopped,  and  the  fire  is  banked.  The 
furnace  cools  slowly,  as  otherwise  the  pots  would  be  liable  to 
crack,  and  in  the  course  of  a  week  or  more  the  furnace  is  cold 
enough  to  allow  the  entrance  of  the  workmen  by  the  manhole, 
which  has  been  opened.  The  wheelswarf  cover  is  broken  and 
removed,  and  the  bars  are  taken  out  of  the  pot. 

The  charging,  converting,  and  unpacking  occupy  about 
three  weeks :  for  higher  carbonisation  more  time  is  required 
than  for  lower  temper  bars.  About  25  tons  of  coals  will  be 
consumed  during  the  conversion  of  an  ordinary  30-ton  lot  of 
bars. 

During  conversion  the  bars  gain  in  weight  through  carbon 
being  taken  up.  The  "  converted  "  or  "  cemented  "  bars 
differ  in  appearance  from  the  bars  as  packed.  Originally 
they  were  fibrous  and  tough.  As  taken  from  the  boxes  they 
are  crystalline*  and  brittle,  and  are  covered  with  blisters — 
hence  the  name  "  blister  steel."  If  the  blisters  are  small  and 
evenly  distributed  over  the  surface,  it  is  assumed  that  the 
iron  was  good  and  that  the  conversion  is  satisfactory. 

The  blister  steel  bars  are  broken  across;  the  fracture  is 
examined,  and  each  piece  is  stacked  according  to  its  "  temper  " 
or  degree  of  carburisation.  The  bars  which  were  nearest  to 
the  fire  are  more  highly  carburised  than  those  which  were  in 
the  centre  of  the  pot,  and  there  must  necessarily  be  more 
than  one  temper  from  each  pot. 

In  the  trade  the  blister  steel  is  classed  thus — 

No.  1  or  spring  heat,   containing  £  or     *5  per  cent,  of  carbon. 
2       country  heat,         ,  |  „     '625 


single  shear  heat,  , 
double  shear  heat,  , 
steel- through  heat, , 


"75 
1'25 


melting  heat, 

No.  1  is  not  called  "  spring  heat "  to  indicate  that  it  is 
suitable  for  making  springs  (it  is  not  suitable),  but  because  of 

*  In  the  lower  tempers  the  centre  portion  remains  uncarbonised  and 
is  called  "sap";  the  crystals  of  sap  have  lost  their  brilliancy — the 
sap  is  said  to  be  killed  and  no  longer  looks  "  raw  "  or  "  stares."  " 


STEEL    FOR   TOOLS   AND   CUTLERY.  41 

so  much  "sap."  The  term  "Irish  temper"  is  also  applied 
and  the  term  "  country  heat,"  by  which  No.  2  is  known,  are 
all  suggestive  of  verdancy.  In  the  lower  numbers  the  con- 
version has  not  proceeded  far,  and  the  broken  bars  show 
much  unaltered  iron  in  the  centre.  In  "  double  shear  heat " 
bars  about  one-half  of  the  area,  in  the  centre,  has  not  been 
changed,  while  in  the  highest  number  the  whole  of  the  bar 
has  been  converted,  all  the  fibre  has  gone,  and  the  entire 
area  of  the  fracture  is  crystalline. 

Even  with  experience  and  the  exercise  of  care  accidents 
occasionally  happen,  and  the  cemented  bars  are  more  or  less 
spoiled.  Aired  bars  are  those  to  which  air  has  had  access 
through  a  crack  or  cracks  in  the  pot  or  the  covering.  Glazed 
bars  are  those  which,  during  conversion,  have  been  over- 
heated, and  the  edges  of  which  are  generally  melted  in  the 
converting  pot.  Flushed  bars  are  those  resulting  from  over- 
hurried  conversion,  and  which  show  too  plainly  the  lines 
dividing  converted  from  unconverted  portions.  Tradition 
tells  of  "  pots  "  which  were  so  badly  cracked  that  the  charcoal 
had  been  burned  and  the  intense  local  heat  had  caused  the 
bars  to  become  welded  together.  But  the  bars,  as  a  rule, 
successfully  run  the  gauntlet  of  possible  mishaps,  and  the 
product  is  good  for  the  intended  purpose.  The  majority  of 
the  blister  steel  bars  are  meant  to  be  melted  in  crucibles. 
Some,  however,  are  to  be  used  otherwise,  and  they  are  sub- 
jected to  different  treatment. 

"  Bar  Steel  is  the  name  given  to  blister  steel  which  has  been 
tilted  or  rolled  down  to  the  size  required. 

"Single  Shear  Steel  is  produced  by  welding  six  bars  of 
blister  steel  which  are  unconverted  in  the  centre,  and  rolling 
them  down  so  as  to  have  a  fairly  uniform  mixture  of  iron  and 
steel — a  material  which  combines  great  tenacity  with  the 
capability  of  carrying  a  moderately  hard  shearing  or  cutting 
edge."  Or  bars  of  blistered  steel  may  be  heated  and  ham- 
mered into  plates,  an  operation  known  as  plating.  Seven  or 
eight  plates  are  piled  together,  heated,  and  hammered  into 
shape.  In  some  instances  they  are  finally  rolled  down  into 
single  shear  blades. 

"Double  Shear  Steel  is  produced  by  rolling  down  single 
shear  steel  to  suitable-sized  bars  and  rewelding  two  of  them 


42  IRON   AND    STEEL    MANUFACTURE. 

together  so  that  the  mixture  of  iron  and  steel  may  be  more 
perfect."*  Or  hammered  shear  steel  is  bent  over  on  itself, 
and  again  hammered  down. 

The  bars  or  plates  require  to  be  raised  to  a  welding  heat, 
and  must  be  protected  to  prevent  undue  and  uneven  loss  of 
carbon.  For  this  purpose  the  bars  or  piles  are  covered  with 
gypsum  or  other  suitable  material  which  will  melt  and  form 
an  even  coating  capable  of  remaining  intact  while  in  the 
furnace. 

Cast  or  Crucible  Steel. — Blister  steel  bars  contain  slag,  and 
no  bar  is  uniform  in  composition  throughout.  The  outer 
portions  of  each  contain  more  carbon  than 
the  inner  portions.  To  obtain  a  homo- 
geneous! steel,  from  which  the  slag  has 
become  separated,  it  is  necessary  to  melt  the 
blister  steel. 

Melting  is  carried  on  in  crucibles  or 
"pots,"  which  are  carefully  made  from 
judicious  mixtures  of  suitable  fireclay.  A 
crucible  is  about  1 7  inches  high  and  7  or  8 
inches  diameter  at  the  top.  They  are 
seasoned  for  a  fortnight  or  so  and  "annealed" 
before  being  used. 
Fig.  19.— Crucible* 

Stand.Lld  and  The  "steel-melting  house,"  in  which  the 
making  of  crucible  cast  steel  is  carried  on, 
is  a  building  which  contains  a  number  of  "  steel-melting 
holes,"  and  the  necessary  arrangements  for  casting  the  steel 
into  ingots.  Fig.  20  shows  a  view  of  a  steel-melting  house 
at  the  works  of  Messrs.  Samuel  Osborn  &  Co.,  Sheffield— 
so  long  associated  with  the  Mushets.  The  steel-melting  holes 
are  ranged  along  the  sides  of  the  building  but  under  the 
floor  level.  They  are  covered,  as  shown  in  the  illustration, 
by  covers  composed  of  firebrick  slabs  set  in  iron  frames  and 
having  iron  handles. 

A  section  of  a  steel-melting  hole  is  shown  in  fig.  2 1 .  Each 
"hole,"  or  furnace,  is  lined  with  ganister  so  as  to  form  an 

*  Seebohm,  Iron  and  Steel  Inst.  Journal,  1 884,  ii. ,  p.  379. 
fFrom  Greek  words  signifying  of  one  kind. 


44 


IRON    AND    STEEL    MANUFACTURE. 


oval  of  about  36  inches  in  depth,  26  inches  in  its  longest 
diameter,  and  19  inches  across,  so  as  to  hold  two  crucibles  or 
pots.  Access  to  the  fire-bars,  &c.,  is  from  the  cellar.  Ten 
or  more  holes  constitute  a  set,  the  flues  from  which  lead  to 
long  stacks. 

The  fuel  used  is  a  specially  hard  burned  coke,  and  the 
draught  from  the  furnace  is  regulated  in  a  simple  manner 


Fig.  21.— Section  of  Steel-melting  Hole. 


A,  Crucible  being  gently  dried. 

B,  Shelf  and, support. 

C,  Stack. 

D,  Cover  of  melting-hole. 

E,  Handle  of  cover. 

F,  Furnace. 

G,  Lid. 


H,    Crucible. 
I,  I,  Flues. 
J,     Stand. 

Fire-bar. 

Bearer. 


K, 
L, 


M,   Brick  for  regulating  the 
draught. 


which  is  quite  effective.  If  the  temperature  requires  to  be 
moderated,  the  brick  which  is  used  for  closing  the  inlet*  from 
the  cellar  flue  (see  fig.  21)  is  removed,  thus  allowing  an 
inrush  of  cold  air  through  the  flue  to  the  chimney.  The 


STEEL    FOB   TOOLS    AND    CUTLERY.  45 

"  draught  "  is  thereby  lessened.  When  a  higher  temperature 
is  needed  the  brick  is  inserted  in  the  inlet.  Only  hot 
products  of  combustion,  or  hot  air  which  has  passed  between 
masses  of  glowing  coke,  can  enter  the  flue,  and,  as  the  chimney 
thereby  becomes  and  continues  to  be  filled  with  hot  gases,  the 
draught  is  increased.  Live  coals  are  used  to  kindle  the  coke 
required  as  fuel  in  the  melting  holes. 

The  crucibles  employed  in  steel  melting  are  carefully 
prepared  beforehand,  and  are  subjected  to  a  long  course  of 
gentle  drying.  Before  being  used  they  are  kept,  mouth 
downwards,  in  an  annealing  furnace  which  is  at  a  red  heat. 
The  pot,  which  has  thus  been  tempered,  is  set  on  a  stand 
in  a  hot  melting  hole  and  coke  is  packed  round  it.  In  the 
course  of  an  hour  the  pot  is  ready  for  the  charge.  To 
charge  the  pot,  one  workman  holds  a  wrought-iron  funnel 
or  charger,  while  another  empties  a  weighed  charge  of  blister 
steel — of  selected  temper — which  is  in  small  pieces.  The 
charge  also  contains  some  fluxing  material  and  some  "  physic." 
Physics  are  compounds  containing  manganese,  a  metal  which 
acts  beneficially  in  steel-making.  The  lid  is  then  put  on  the 
crucible.  The  next  one  is  charged  in  like  manner,  the  re- 
mainder of  the  hole  is  filled  in  with  coke,  the  cover  is  placed 
over  the  hole,  and  the  draught  is  regulated.  When  the  fire 
has  burned  some  time  the  remainder  of  the  coke  in  the  hole  is 
pottered  down  towards  the  fire-bars,  and  more  coke  is  added. 

From  time  to  time  the  head  melter  examines  the  condition 
of  the  furnaces  and  gives  orders  for  the  further  making-up  of 
the  fires,  the  regulation  of  the  draught,  &c.  By  and  bye  he 
has  the  covers  moved,  and,  feeling  with  an  iron  rod  the 
contents  of  the  crucibles,  he  gives  final  instructions  with 
regard  to  the  fires  and  the  time  of  teeming.  The  head 
melter  must  have  ripe  experience  and  sound  judgment. 
When  ready,  the  "  puller-out,"  wrapped  in  "  clothes "  which 
are  soaked  in  water  to  protect  him  from  the  heat,  lowers 
a  pair  of  tongs,  with  a  broadened  and  ribbed  ending,  into 
the  furnace  and  with  them  grips  one  of  the  crucibles,  pulls 
it  up,  and  sets  it  on  the  floor  of  the  melting  house.  The 
slag  is  quickly  skimmed  off,  and  the  steel  is  poured  into 
the  moulds.  The  moulds  are  of  cast  iron  and  each  formed  of 
two  halves  tightly  held  together  by  rings  and  wedges.  The 


46  IRON    AND    STEEL    MANUFACTURE. 

moulds  must  be  previously  "reeked"  (smoked)  or  covered 
with  a  fine  deposit  of  soot  by  exposing  the  inner  surfaces  to 
the  smoky  flame  of  burning  coal  tar.  Or  the  steel  may  be 
prevented  from  adhering  to  the  moulds  by  wiping  the  inner 
parts  with  oil  or  with  fireclay  in  water.  The  moulds  must 
be  dry  and  warm  before  teeming  the  steel  into  them.  They 
are  set  in  a  slanting  position  in  recesses — known  as  "  teeming 
holes  " — in  the  floor,  and  the  steel  is  poured  into  them.  The 
crucible  is  then  put  back  into  the  furnace,  or  hole,  and  heated 
before  receiving  the  next  charge. 

The  first  crucible  charge  for  the  day  may  be  60  Ibs.,  the 
second  one  54  Ibs.,  and  the  third  one  48  Ibs.  These  three 
charges  constitute  the  round  for  the  day  and  finish  the  life  of 
the  crucible,  which  cannot,  with  a  reasonable  degree  of  safety, 
be  trusted  to  melt  more.  Each  crucible  is  placed  in  a  hot 
oven  about  24  hours  before  being  required  so  that  it  may  be 
well  annealed  before  receiving  its  charge.  Owing  to  chemical 
action  which  cuts  a  groove  into  the  crucible  where  the  slag  is — 
on  the  top  of  the  melted  steel — it  is  necessary  to  diminish  the 
weight  of  the  second  and  third  charges  in  each  pot. 

Inferior  steel  must  be  "  teemed  "  into  tfye  mould  as  soon  as 
possible  after  it  has  become  perfectly  fluid  and  as  hot  as  the 
pot  is  likely  to  stand  the  strain  of  "pulling  out."  Higher 
class  steel  requires  "  killing  " — that  is,  it  requires  to  be  kept  in 
the  furnace  for  about  half  an  hour  (more  or  less  as  the  judg- 
ment of  the  head  melter  decides)  after  it  has  become  fluid, 
and  it  must  be  poured  at  a  proper  temperature.  The  higher 
the  quality  of  the  steel  the  more  killing  it  will  require.  If 
not  "  killed,"  or  if  too  hot  when  poured,  the  steel  boils  over 
in  the  mould,  the  fracture  of  the  ingot  when  cold  shows  a 
series  of  bubbles  like  a  sponge.  "If  the  steel  be  not  long 
enough  in  the  fire,  it  will  teem  fiery  and  produce  a  honey- 
combed ingot,  and  the  'same  result  will  follow  if  it  be  too  hot 
when  it  is  poured.  If  it  remain  too  long  in  the  fire  it  will 
teem  '  dead,'  the  fracture  of  the  ingot  will  look  scorched,  and 
though  exceptionally  sound  it  will  be  brittle  if  hard,  and 
wanting  in  tensile  strength  if  mild.  If  the  molten  steel  be 
chilled  before  it  is  poured  into  the  mould,  which  may  be 
detected  by  the  stream  skimming  over  as  it  is  teemed,  the 


STEEL    FOR   TOOLS    AND   CUTLERY. 


47 


fracture  of  the  ingot  will  appear  dull  in  colour,  and  full  of 
small  holes  and  honeycombs."  * 

The  steel  ingots  are  carefully  reheated  and  hammered  or 
rolled  into  the  bars  required.  Bars  for  certain  purposes  are 
straightened  by  reeling. 

The  lest  crucible  cast  steel  is  made  from  Swedish  iron,  smelted 
from  ores  containing  a  small  quantity  of  phosphorus. 

There  are  four  methods  of  making  crucible  steel,  and  they 
are  as  under  : — 

I.  Select  cut  bar  iron  and  "fetch  it  up"  by  addition  of 
charcoal.     Melt  and  teem. 

II.  Use  broken  pig  iron  and  "  let  it  down  "  to  the  required 
temper  with  cut  bar  iron.     Melt  and  teem. 

III.  Select  or  "take  up"  blister  steel  of  the  desired  per- 
centage of  carbon.     Melt,  dead  melt  or  kill,  and  teem. 

IV.  Select  blister  steel  which  is  a  little  too  hard  and  "  let 
it  down"  with  a  small  quantity  of  milder  cast  steel  scrap. 
Melt,  dead  melt  or  kill,  and  teem. 

Some  steel-makers  believe  that  only  by  methods  III.  and 
IV.  can  best  quality  steel  be  made  in  crucibles. 

TABLE  OF  THE  COMPOSITION  OF  THE  "METAL"  IN  THE  VARIOUS 
STAGES  OF  THE  MANUFACTURE  OF  CRUCIBLE  CAST  STEEL. 


Chemi- 

Swedish 

Cemented 

Constituents. 

cal 
Sym- 

Swedish 
Pig  Iron. 

Wrought- 
iron 

Bars, 
or  Blister 

Crucible 
Cast  Steel. 

bols. 

Bars. 

Steel. 

Graphitic  carbon, 

c 

0-12 

Combined  carbon, 

c 

3-86 

6-05 

variest 

variest 

Silicon, 

Si 

0-15 

002 

0-02 

0-17 

Phosphorus, 

P 

0-03 

0-02 

0-02 

0-02 

Sulphur, 

s 

0-02 

o-oi 

o-oi 

0-05 

Manganese, 

Mn 

0-29 

0-07 

0-07 

0-18 

Iron,    . 

Fe 

A 

A 

A 

A 

100-00 

100-00 

100-00 

100-00 

*  Seebohm,  Iron  and  Steel  Institute  Journal,  ii.,  1884,  p.  385. 
fThe  percentage  of  carbon  varies  according  to  the  treatment  in  the 
cementation  process,  as  previously  explained. 


48  IRON   AND   STEEL    MANUFACTURE. 

The  chief  points  in  the  foregoing  table  are  :  — 

The  Swedish  pig-iron  contains  little  phosphorus  and 
less  sulphur.  The  carbon,  silicon,  and  manganese  —  and 
to  a  slight  extent  the  sulphur  —  are  reduced  in  amount 
during  the  working  of  the  pig  iron  into  wrought-iron 
bars,  and  it  may  here  be  explained  that  it  is  absolutely 
necessary  to  remove  the  excess  silicon,  which  is  un- 
avoidably present  in  the  pig  iron.  It  is  not  practicable 
to  get  rid  of  even  that  small  quantity  of  silicon  without 
removing  carbon  and  manganese. 

The  only  change  effected  during  the  cementation  stage 
is  the  combination  of  carbon  with  the  iron  —  with  pro- 
duction of  blister  steel.  While  in  the  crucible  the  steel 
is  increased  in  manganese,  sulphur,  and  silicon. 

The  increase  in  sulphur  arises  from  the  presence  of  that 
element  in  the  coke  used  as  fuel.  Sulphur  can,  singularly 
enough,  penetrate  the  hot  crucible,  and  combine  with  the 
metal.  The  additional  manganese  is  derived  from  the  ferro- 
manganese*  or  other  physic  /  used.  Manganese  acts  on  the 
oxide  of  iron  remaining  in  the  steel,  liberating  the  iron 
and  becoming  oxide  of  manganese  —  a  reaction  indicated  by 
the  equation  — 

FeO          +          Mn  =       Fe       +  MnO 

Iron  oxide  and  manganese   yield    iron    and      -j     oxir  e  J 

The  oxide  of  manganese  rises  to  the  top  of  the  metal  and 
attacks  the  silica  of  the  crucible,  manganese  silicate  being 
formed.  During  dead  melting  or  killing,  this  silicate  is  acted 
on  by  carbon  in  the  steel  with  liberation  of  silicon.  The 
reaction  may  be  represented  thus  — 

2MnO,SiO2       +         C  Si        +         CO2        +          2MnO 

«ietd 


This  silicon  passes  into  the  steel,  and  effects,  or  at  least 
hastens,  the  elimination    of   gases.     The    small    quantity    of 
silicon  which  is  taken  up  is  beneficial,  but  more  than  that 
*  See  composition  on  p.  237. 


STEEL    FOR    TOOLS    AND    CUTLERY  49 

amount  would  be  deleterious.  The  small  percentage  of 
manganese  does  not  adversely  affect  the  quality  of  the  steel, 
while  it  is  helpful  in  keeping  down  the  evil  influence  of  the 
sulphur  which  has  entered  the  steel.  Good  crucible  steel 
cannot  be  made  from  iron  containing  more  than  '03  per  cent, 
of  phosphorus ;  hence  the  great  value  of  the  comparatively 
pure  Swedish  irons. 

For  cheap  cutlery  or  for  constructive  purposes  "steel"  is  often 
made  in  crucibles  from  materials  other  than  cemented  bars 
with  a  judicious  addition  of  black  oxide  of  manganese  along 
with  a  little  carbon,  or  the  addition  of  spiegel-eisen — which  is 
a  fairly  pure  white  pig  iron  containing  much  manganese — or 
the  still  richer  ferro-manganese.  Then  there  is  the  un- 
challenged statement  of  the  late  Sir  Henry  Bessemer  that 
"  at  least  one-half  of  the  crucible  steel  made  in  Sheffield  is 
made  from  Bessemer  scrap,  simply  remelted."*  For  some  pur- 
poses such  steel  scrap  is  remelted  in  graphite  (plumbago) 
crucibles.  Puddled  steel — a  semi-puddled  product — is  also 
used  in  making  crucible  steel,  and  steel  is  made  from  un- 
converted bars  by  melting  a  charge  and  adding  carbon  and 
spiegel-eisen. 

Besides  such  "physics"  as  spiegel-eisen  and  ferro-manganese, 
quite  a  number  of  nostrums  have  been  proposed  at  various 
times  and  used  in  attempting  to  make  superior  steels  from 
common  iron. 

A  large  quantity  of  steel  is  made,  the  chief  quality  of  which 
is  the  possession  of  an  enduring  cutting  edge.  Some  crucible 
steel  ingots  are  required  to  be  solid ;  some  mild  steels  must 
be  weldable. 

The  first  successful  attempt  to  improve  the  quality  of 
crucible  cast  steel  for  tools  was  made  by  11.  F.  Mushet, 
whose  "self-hardening"  tool  steels  (steels  containing  chro- 
mium, tungsten,  and  a  notable  amount  of  manganese)  held 
the  field  until  the  advent  of  the  "  rapid  -  cutting "  tools 
of  Messrs,  Taylor  &  White,  of  the  Bethlehem  Company's 
Works,  Pennsylvania,  U.S.A.,  paved  the  way  for  further 
considerable  advances  in  the  quality  of  quick-cutting  tools. 
*  Iron  and  Steel  Journal,  1884,  vol.  ii.,  p.  397. 


60  IBON    AND    STKEL    MANUFACTURE. 

Analysis  of  Special  Tool  Steels. — Mushet's  self-hardening  tool 
steel  contains  carbon,  1'65  ;  silicon,  1'36  ;  manganese,  2'12  ; 
tungsten,  5 '80  ;  and  chromium,  0'45  per  cent. 

Quick-cutting  steel,  as  made  by  Messrs.  Whitworth,  Arm- 
strong &  Co.,  Manchester,  contains  carbon,  0'55  ;  tungsten, 
13 *5  ;  and  chromium,  3*5  per  cent. 

To  all  steel  users  the  good  advice  given  in  Metcalfe's  excel- 
lent Manual  for  Steel  Users  can  be  commended :  "  The  best 
way  for  a  steel  user  to  do  is  to  tell  the  steel-maker  what  he 
wants  to  accomplish  and  put  upon  him  the  responsibility  of 
selecting  the  best  temper.  It  costs  no  more  to  make  and  to 
provide  one  temper  than  another ;  therefore  the  one  induce- 
ment of  the  steel-maker  is  to  give  his  patron  that  which  is 
best  adapted  to  his  use." 

The  most  useful  tempers  of  tool  steel  are  included  in  the 
following  list,  compiled  by  the  late  Mr.  H.  Seebohm : — 

Razor  Temper  (1£  per  cent.  Carbon). — This  steel  is  so  easily  burnt 
by  being  overheated  that  it  can  only  be  placed  in  the  hands  of  a  very 
skilful  workman.  When  properly  heated,  it  will  do  twice  the  work  of 
ordinary  tool  steel  for  turning  chilled  rolls,  &c. 

SawJUe  Temper  (If  per  cent.  Carbon). — This  steel  requires  careful 
treatment ;  and,  although  it  will  stand  more  fire  than  razor-steel, 
should  not  be  heated  above  a  cherry-red. 

Tool  Temper  (1£  per  cent.  Carbon). — The  most  useful  temper  for 
turning  tools,  drills,  and  planing- machine  tools  in  the  hands  of  ordinary 
workmen.f  It  is  possible  to  weld  cast  steel  of  this  temper,  but  only 
with  the  greatest  care  and  skill. 

Spindle  Temper  (1£  per  cent.  Carbon). — A  very  useful  temper  for 
circular  cutters,  very  large  turning  tools,  taps,  screwing  dies,  &c. 
This  temper  requires  considerable  care  in  welding. 

Chisel  Temper  (1  per  cent.  Carbon). — An  extremely  useful  temper, 
combining,  as  it  does,  great  toughness  in  the  unhardened  state  with 
the  capacity  of  hardening  at  a  low  heat.  It  is  consequently  well 
adapted  for  tools  when  the  unhardened  part  is  required  to  stand  the 
blow  of  a  hammer  without  snipping,  but  where  a  hard  cutting  edge  is 
required,  such  as  cold  chisels,  hot  setts,  &c. 

Sett  Temper  (§  per  cent.  Carbon). — This  temper  is  adapted  for  tools 
where  the  chief  punishment  is  on  the  unhardened  part,  such  as  cold 
setts,  which  have  to  stand  the  blows  of  a  very  heavy  hammer. 

Die  Temper  (f  per  cent.  Carbon). — The  most  suitable  temper  for 
tools  where  the  surface  only  is  required  to  be  hard,  and  where  the 
capacity  to  withstand  great  pressure  is  of  importance,  such  as  stamping 
or  pressing  dies,  boiler  cups,  &c.  Both  the  two  last  tempers  may  be 
easily  welded  by  a  mechanic  accustomed  to  weld  cast  steel. 


CHAPTER  V. 
TREATMENT  OF  TOOL  STEEL. 

SPECIAL  CHAPTER  BY  H.  W.  WALDRON. 

WHEN  a  steel  containing  more  than  about  0'2  per  cent,  of 
carbon  is  heated  to. redness,  and  suddenly  cooled  by  quenching 
in  water  or  other  suitable  medium,  it  becomes  hard.  The 
degree  of  hardness  depends  to  a  certain  extent  upon  the 
rapidity  of  cooling  and  the  temperatures  used,  but  to  a  much 
greater  extent  upon  the  percentage  of  carbon  contained  in  the 
steel.  Steels  containing  0'2  per  cent,  of  carbon  can  only  be 
slightly  hardened  by  the  above  treatment,  while  those  con- 
taining from  I'OO  to  1'75  per  cent,  become  intensely  hard 
and  somewhat  brittle. 

Several  theories  have  been  advanced  in  explanation  of  the 
phenomenon  of  hardening,  but  whatever  may  be  the  precise 
function  of  the  carbon,  it  is  agreed  that  the  presence  of  that 
element  is  essential  to  the  hardening  of  ordinary  commercial 
steel. 

The  changes  observable  during  the  heating  and  cooling  of 
steel  may  be  thus  briefly  summarised  : — When  a  piece  of 
almost  carbonless  iron,  heated  to  about  900°  C.  (full  cherry 
red),  is  allowed  to  cool  slowly,  and  its  temperature  continually 
recorded  by  a  sensitive  pyrometer,  it  is  found  that  a  "  retarda- 
tion "  in  the  rate  of  cooling  takes  place  at  three  distinct  points, 
indicating  that  a  chemical  or  physical  change  has  taken  place 
with  evolution  of  heat.  These  critical  points — which  occur  at 
temperatures  of  about  825°  C.  (cherry  red),  720°  C.  (low  red), 
and  650°  C.* — are  known  by  the  formulae  Ar  3,  Ar  2,  and 
Ar  1.  In  the  case  of  steels  containing  a  considerable  per- 
centage of  carbon,  there  is  only  one  critical  point,  Ar  1,  at 
about  670°  C.*  The  reverse  changes  take  place  during  the 
heating  up  of  steel,  there  being  an  absorption  of  heat  at  the 

*  825°  Centigrade  =  1,517°  on  the  ordinary  (Fahrenheit)  thermometer. 
720°        „  =1,328" 

670°        „  =1,238° 

650°  =1,202° 


52  IRON    AND   STEEL    MANUFACTURE. 

points  Ac  1,  Ac  2,  Ac  3,  which  occur  about  30°  C.  above 
those  observable  on  cooling  down  the  steel. 

The  retardation  taking  place  at  Ar  1  is  accompanied  by  a 
change  in  the  condition  of  the  carbon  from  the  state  of 
"  hardening  carbon,"  as  it  exists  in  hardened  steel,  to  that  of 
"  cement  carbon,"  or  the  definite  carbide,  Fe3C,  which  is  pre- 
sent in  normal  and  annealed  steel.  In  order  to  convert 
cement  carbon  into  hardening  carbon,  it  is  necessary  to  heat 
the  steel  to  a  temperature  above  the  critical  point  Ac  1. 

Brinell,  in  his  famous  researches  on  the  heat  treatment  of 
steel,  used  the  terms  W  and  V  to  indicate  the  points  Ac  1  and 
Ar  1  respectively,  and,  for  the  sake  of  simplicity,  BrmeH's 
formulae  will  be  used  in  the  remainder  of  this  chapter,  which 
will  deal  only  with  steels  containing  '7  per  cent,  and  upwards 
of  carbon,  unless  otherwise  stated. 

If  steel,  heated  to  any  temperature  above  W,*  is  suddenly 
cooled  by  quenching,  the  carbon  is  retained  as  "hardening 
carbon"  (no  time  being  given  for  the  change  to  "cement 
carbon  "  to  take  place),  and  hardened  steel  is  the  result. 

Hardening  of  Steel  in  Practice. — It  would  appear  from  the 
preceding  paragraph  that  the  process  of  hardening  steel  by 
quenching  from  any  temperature  above  a  red  heat  is  an  ex- 
tremely simple  operation.  It  is  true  that  steel  containing  a 
sufficient  amount  of  carbon  may  be  made  quite  hard  by  the 
above  means  without  any  precautions  whatever,  but  nothing 
has  yet  been  said  about  the  strength,  durability,  freedom  from 
defects,  and  general  fitness  of  a  tool  so  hardened.  As  a 
matter  of  fact,  for  the  successful  hardening  of  tool  steel  con- 
siderable skill  and  care  are  needed. 

Brinell  noted  that  when  steel  is  heated  to  the  temperature 
W,  and  either  quenched  or  slowly  cooled,  an  extremely  fine 
grain  is  produced,  and  that,  if  heated  to  any  temperature 
above  W,  the  grain  becomes  coarser  and  coarser  with  each 
increment  of  heat.  No  matter  how  coarse  the  fracture  is 
before  the  treatment,  it  becomes  as  fine  as  it  is  possible  for 
that  steel  to  be  when  it  is  heated  to  the  temperature  W. 

In  hardened  steel  the  finest  structure  is  accompanied  by  the 
greatest  strength. 

*  The  temperature  indicated  by  W  is  about  700°  C.  with  steels  con- 
taining 1£  to  1  ^  per  cent,  of  carbon,  and  gradually  rises  as  the  percentage 
of  carbon  decreases. 


TREATMENT    OF   TOOL    STEEL.  53 

The  following  experiment  is  very  instructive  : — Take  a  bar 
of  tool  steel  (•§-  inch  x  f  inch  x  12  inches  long  is  a  convenient 
size),  notched  with  a  chisel  at  intervals  of  1  inch  throughout 
its  length,  and  heat  it  in  such  a  manner  that  one  end  is  at  a 
bright  yellow  heat,  gradually  decreasing  to  a  temperature 
below  redness  at  the  other  end.  Then  quench  the  bar  in 
cold  water,  break  off  at  the  notches,  and  compare  the  frac- 
tures. It  will  be  found  that  the  part  which  has  been  heated 
to  the  highest  temperature  will  have  a  coarse  granular  frac- 
ture, and  that  the  size  of  the  grains  gradually  decreases  in  the 
parts  less  highly  heated,  until  the  point  heated  to  the  tempera- 
ture W  is  reached,  when  a  fine  fracture  like  that  of  porcelain 
will  be  exhibited. 

Although  steel  may  be  hardened  by  quenching  from  any 
temperature  above  W,  it  will  be  readily  understood  that  the 
temperature  which  gives  the  finest  grain  and  the  greatest 
strength,  together  with  sufficient  hardness,  must  be  the  best  to 
quench  from.  The  correct  hardening  heat  for  any  steel  may 
easily  be  experimentally  determined  by  quenching  samples 
from  different  temperatures  and  observing  the  fractures. 

For  the  successful  hardening  of  tool  steels,  means  must  be 
at  hand  for  gradually  bringing  up  the  metal  to  the  required 
temperature,  allowing  sufficient  time  for  it  to  become  uniformly 
heated  throughout,  but  without  permitting  any  part  of  it  to 
exceed  the  correct  hardening  heat.  Excessive  oxidation 
should  be  carefully  avoided. 

The  means  used  for  heating  are  too  numerous  to  be  detailed 
here ;  any  appliances  may  be  used  which  will  bring  about  the 
conditions  named  above.  They  include  various  forms  of  coal- 
and  gas-fired  furnaces  and  muffles,  lead  baths,  charcoal  and 
"  breeze  "  fires.  The  temperature  may  be  judged  with  the  eye 
with  surprising  accuracy  by  an  experienced  hardener,  but  in 
some  cases  a  pyrometer  may  be  used  with  advantage.  If  a 
pyrometer  is  not  used,  the  light  in  the  hardening  shop  should 
be  subdued  and  as  uniform  as  possible,  all  bright  sunlight  being 
carefully  excluded.  Steel  which  looks  red  hot  in  diffused  day- 
light will  appear  almost  black  in  bright  sunlight.  Excellent 
hardening  is  continually  being  done  from  an  ordinary  black- 
smith's hearth,  but  much  experience  and  judgment  are 
necessary  in  order  to  obtain  good  results  by  this  method. 


54  IRON    AND    STEEL    MANUFACTURE. 

Quenching. — For  most  purposes,  water  is  the  best  quenching 
medium.  The  tool  should  be  kept  moving  rapidly  in  the 
water,  otherwise  bubbles  of  steam  may  collect  on  the  surface 
of  the  steel,  and  greatly  retard  the  cooling  action.  The  water 
should  be,  as  near  as  is  practicable,  to  the  temperature  which 
is  known  to  give  good  results  with  the  class  of  steel  being 
hardened.  Hardening  in  very  cold  water  at  the  commencement 
of  a  day's  work  will  often  result  in  an  unusual  number  of 
cracked  tools. 

Brine  has  a  greater  quenching  power  than  pure  water,  and 
with  some  tools  (notably  files)  gives  better  results. 

Mercury  is  a  quicker  cooling  medium  than  either  water  or 
brine,  and  is  sometimes  used  for  small  articles  required  to  be 
extremely  hard. 

Quenching  in  Oil. — Some  articles,  such  as  springs  and  saws, 
which  are  required  to  be  very  elastic  and  tough  without 
possessing  very  great  hardness,  are  quenched  in  oil.  Whale 
oil  and  lard  oil  are  frequently  used  for  the  purpose. 

Defects  Produced  by  Hardening. — Improper  hardening,  or 
the  use  of  inferior  steel,  will  often  cause  "water  cracks." 
These  cracks  are  the  direct  result  of  the  enormous  stresses  to 
which  the  hardened  steel  is  subjected  by  contraction  during 
the  sudden  cooling.  The  stresses  vary  in  extent  and  direction 
according  to  the  shape  and  size  of  the  tool,  the  temperature  of 
the  steel  and  of  the  quenching  medium.  Sometimes  a  corner 
of  the  steel  will  fly  off  when  in  the  water,  while  in  other  cases 
the  cracks  can  only  be  detected  by  a  very  minute  examination 
of  the  polished  surface  of  the  metal.  If  the  steel  has  been 
tempered  before  the  crack  is  detected,  the  surface  of  the 
fracture  where  the  water  crack  occurs  will  be  covered  with  an 
oxide  film  of  the  usual  temper  colour,  even  if  the  crack  is  so 
minute  as  to  require  the  aid  of  a  magnifying  glass  to  see  it. 

The  necessary  conditions  for  the  prevention  of  water  cracks 
may  be  obtained — 

(1)  By  the  use  of  steel  of  such  a  quality  as  to  give  the 

greatest  strength,  together  with  sufficient  hardness. 

(2)  By  minimising,  by  careful  treatment  in  the  forging 

and  hardening  processes,  the  magnitude  of  the 
stresses  to  which  the  steel  is  subjected  by  sudden 
contraction  when  quenched. 


TREATMENT   OP    TOOL   STEEL.  55 

Tool  steel  should  be  low  in  phosphorus  and  manganese. 
The  effect  of  phosphorus  in  causing  brittleness  in  mild  steels 
is  well  known,  and  this  effect  is  much  accentuated  in  high 
carbon  steels,  in  which  about  O02  per  cent,  only  is  permissible. 
It  is  quite  usual  to  have  0'4  or  0'5  per  cent,  of  manganese 
present  in  mild  steel,  but  in  steel  containing  1  per  cent,  of 
carbon,  0'2  per  cent,  of  manganese  is  sufficient  for  most  pur- 
poses, and  in  some  cases  an  additional  O'l  or  0*15  per  cent, 
of  manganese  will  lead  to  numerous  water  cracks,  although 
the  forging  qualities  of  such  a  steel  may  be  excellent. 

Assuming  that  the  quality  of  the  steel  is  right,  and  that  the 
forging  has  been  carefully  done,  it  is  for  the  hardener  to  see 
that  the  steel  is  in  the  best  possible  condition  to  resist  the 
stresses  put  upon  it,  at  the  moment  it  is  put  into  the  water. 
If  water  cracks  are  to  be  avoided,  the  steel  should  be  quenched 
at  that  temperature  which  gives  the  finest  fracture — i.e.,  the 
lowest  temperature  at  which  the  steel  will  properly  harden — as 
it  is  then  in  the  best  possible  condition  to  resist  the  contraction 
stresses.  The  corners  of  a  tool  should  not  be  allowed  to  reach 
a  higher  temperature  than  the  rest  of  the  steel.  If  by 
accident  any  part  of  the  tool  is  got  too  hot,  it  should  not  be 
allowed  to  cool  down  to  the  proper  temperature  and  afterwards 
quenched,  as  the  steel  will  then  have  a  coarse  grain  corre- 
sponding to  the  highest  temperature  reached,  with  a 
proportionate  loss  of  strength.  The  remedy  in  this  case  is  to 
let  the  steel  cool  down  slowly  and  completely,  and  then  again 
gradually  bring  it  up  to  the  correct  hardening  heat,  by  which 
means  the  grain  will  be  restored  to  the  required  degree  of 
fineness.  With  a  tool  that  has  thick  and  thin  parts,  it  is 
advantageous  to  heat  the  thick  part  first,  in  order  to  prevent 
the  thin  part  becoming  overheated,  and  the  method  of  putting 
it  into  the  water  may  also  be  modified  to  suit  various  shapes. 

Tempering. — The  hardness  produced  by  quenching  in  water 
is  generally  accompanied  by  an  undesirable  amount  of  brittle- 
ness,  which  may  be  removed  by  the  process  of  "  tempering." 
This  is  effected  by  reheating  the  hardened  steel  to  a 
temperature  very  much  below  that  required  for  hardening, 
and  varying  in  practice  between  about  220°  C.  and  320°  C.* 

*220°  C.  =  428°  on  the  ordinary  (Fahrenheit)  thermometer. 
320°  C.  =  608° 


56  IRON    AND    STEEL    MANUFACTURE. 

The  degree  of  temper  is  generally  judged  by  an  observation 
of  the  oxidation  tints  which  appear  on  the  bright  surface  of 
the  metal  when  heated,  and  which  succeed  each  other  in  the 
following  order  : — Light  straw,  dark  straw,  brown,  brown  with 
purple  (pigeon  wing),  purple,  blue.  Professor  Turner*  has 
shown  that  the  whole  of  these  tints  may  be  produced  in 
succession  by  keeping  the  metal  at  a  constant  temperature  as 
low  as  220°  C.  for  a  sufficient  length  of  time,  a  very  light 
straw  being  produced  in  two  minutes,  and  a  dark  blue  in  l'2S 
minutes,  at  that  temperature. 

After  tempering,  the  article  may  either  be  allowed  to  cool 
naturally  in  the  air,  or  may  be  quenched  in  water.  With 
some  tools,  such  as  chisels,  the  point  only  is  hardened,  and 
the  tempering  is  effected  by  allowing  the  heat  from  the  hot, 
unhardened  portion  to  travel  to  the  point  until  the  desired 
colour  is  obtained,  when  the  tool  is  quenched  to  prevent  the 
point  becoming  softened.  The  tint  cannot  therefore  be  re- 
garded as  a  reliable  indication  of  the  temperature  obtained 
when  tempering  a  tool,  and  the  use  of  a  thermometer  is  to  be 
preferred  where  practicable. 

Oil-hardened  tools  are  usually  tempered  by  heating  up  until 
the  oil  begins  to  char  or  burn,  this  being  an  indication  of  the 
temperature  reached. 

*  Trans,  of  the  Birmingham  Philosophical  Society,  vol.  vi. ,  Part  2. 


57 


CHAPTER  VI. 
MILD     STEEL. 

MILD  steel  contains  much  less  carbon  than  is  found  in  tool 
steel.  To  avoid  cold-shortness  and  red-shortness  (see  p.  8), 
the  percentage  of  phosphorus  and  of  sulphur  must  each  be 
kept  under  0'05  per  cent,  for  good  quality  steel.  In  regard 
to  these  elements,  mild  steel  is  not  so  pure  as  steel  for 
cutlery  and  tools,  which,  it  may  be  remembered,  contain  only 
0*03  per  cent,  of  each  of  these. 

It  differs  from  wrought  iron  in  percentage  composition,  and, 
in  a  more  marked  degree,  in  its  structure.  Mild  steel  is  finely 
crystalline,  and  is  free  from  slag ;  wrought  iron  is  fibrous,  and 
contains  a  considerable  bulk  of  slag  in  a  state  of  irregular 
intermixture.  Owing  to  the  high  temperature  at  which  mild 
steels  are  finished,  the  metal  is  so  fluid  as  to  allow  of  the 
ready  separation  of  the  slag ;  indeed,  it  was  owing  to  its  being 
"  poured "  in  a  state  of  fluidity  that  the  term  "  steel "  was 
applied  to  it.  The  name  "ingot  iron"  was  proposed,  but  did 
not  prove  acceptable. 

COMPOSITION  OF  WROUGHT  IRON  COMPARED  WITH  STEEL. 


Mild  Steel 

Constituents. 

Chemical 
Symbols. 

Good 
Wrought-Iron 
Shaft. 

for  General 
Engineering 
Purposes. 

Carbon,    . 

c 

trace. 

0-18 

Silicon,     . 

Si 

0-12 

0-02 

Sulphur,  . 

s 

0-04 

0-05 

Phosphorus, 

p 

0-21 

0-05 

Manganese, 
Cinder  or  slag, 

Mn 

trace. 
1-30 

0-50 
none. 

Iron  (by  difference), 

Fe 

A 

A 

100-00 

100-00 

Phosphorus  in  the  Cinder,  0'05. 


58  IRON   AND    STEEL    MANUFACTURE. 

Sir  William  Siemens  showed  the  relative  bulk  of  iron  and 
cinder  in  wrought  iron  by  a  cube  of  4  i -inch  side  representing 
the  iron,  and  one  of  2-inch  side  representing  the  cinder. 
Presence  of  cinder  seriously  impairs  the  tensile  strength  of 
wrought  iron.  Wrought  iron  has  considerable  compensation 
in  its  fibrous  character,  which  cannot  be  imparted  in  the 
absence  of  cinder. 

Mild  steel  is  produced  in  large  quantities  by  the  following 
processes : — 

Bessemer  process,         .  .  \  either 

Siemens  process,           .  .  I  acid 

Martin  process,  .         .  .  f    or 

Siemens-Martin  process,  .  ;  basic. 

It  has  largely  taken  the  place  of  wrought  iron  because — 

(a)  It  can  be  produced  in  larger  masses, 
(&)  It  is  more  uniform  in  composition  throughout  its 
mass, 

(c)  It  has  greater  tensile  strength,  and 

(d)  Its  price  is  lower. 

BESSEMER  PROCESS.  — The  history  of  the  Bessemer  process 
is  most  interesting,  but  cannot  be  dealt  with  here  further 
than  to  state  that  BESSEMER  at  first  intended  to  improve 
the  strength  and  character  of  cast  iron  for  cannons.  His 
investigations  led  him  to  attempt  to  make  tool  steel.  That, 
however,  was  not  continued.  The  manufacture  of  a  material 
suited  to  general  engineering  purposes  offered  a  much  larger 
field,  which  he  proceeded  to  occupy.  Signal  failure  followed 
his  first  success,  but  by  persevering  he  ultimately  triumphed, 
and  produced  the  useful  material  now  known  as  mild  steel. 

We  must  admire  in  Sir  HENRY  BESSEMER  his  ingenuity  in 
following  up  and  improving  on  the  results  of  his  investigations, 
the  genius  displayed  in  devising  suitable  contrivances  for 
carrying  on  the  process,  his  quiet  determination,  his  honesty, 
thoroughness,  and  business  capacity,  as  well  as  his  generous 
acknowledgment  of  the  assistance  of  R.  F.  MUSHET  and  WM. 
HENDERSON  in  helping  him  to  perfect  his  method  of  making 
mild  steel. 


MILD    STEEL.  59 

Briefly,  the  Bessemer  Process  consists  in  blowing  air 
through  fluid  pig  iron,  and  "finishing"  the  metal  according 
to  requirements.  The  metalloids  (see  p.  7)  are  oxidised,  and 
thereby  separated  from  the  iron.  It  is  a  beautiful  process, 
and  is  fully  described  in  the  following  chapters. 


Sir  Henry  Bessemer. 

The  Siemens  Process  consists  in  melting  pig  iron,  and, 
when  the  silicon  and,  incidentally,  the  manganese  have  been 
oxidised,  feeding  suitable  ore  into  the  mass  of  melted  metal 
in  the  furnace.  The  oxygen  in  the  ore  hastens  the  burning 
out  of  the  carbon.  At  the  same  time  the  iron  oxide  in  the 
ore  is  reduced,  the  iron  thereof  adding  to  the  weight  of  ingot 
produced. 

The  skilful  adaptation  of  the  regenerative  system  intro- 
duced in  the  open-hearth  furnace  designed  by  Mr.  FREDERICK 
SIEMENS  (brother  of  Sir  WILLIAM  SIEMENS)  has  deservedly 
won  most  hearty  commendation. 


60  IRON    AND    STEEL    MANUFACTURE. 

Martin  Process. — The  steel-making  process  with  which  the 
name  of  M.  Martin  is  associated  consists  in  melting  together 
scrap  steel,  or  good  scrap  wrought  iron,  with  a  quantity  of 
pig  iron,  and  allowing  oxidation  to  proceed.  It  may  have 
been  suggested  by  the  method  devised  by  Reaumur  in  the 
year  1722. 

The  Siemens-Martin  process  is  a  combination  of  the  two 
methods  briefly  described  above.  Siemens-Martin  steel  is 
often  called  Siemens  steel,  and  as  it  is  always  produced  in 
open-hearth  furnaces  it  is  known  as  open-hearth  steel. 


Sir  William  Siemens. 

Unless  basic  steel  is  specified  it  is  generally  understood 
that  acid  steel  is  meant — just  as  Mr.  Smith  (the  senior)  is 
meant  unless  Mr.  Smith,  junior,  is  mentioned.  This  remark 
applies  alike  to  Bessemer  and  Siemens  steels. 

SIEMENS-MARTIN  STEEL  is  in  great  demand  because  it  is 
a  reliable  material  possessing  valuable  properties.  It  is  made 
from  the  same  class  of  pig  iron  as  acid  Bessemer  steel ;  and, 
so  far  as  the  content  of  carbon,  phosphorus,  sulphur,  and 
manganese  is  concerned,  the  two  steels  are  frequently  identical 
in  composition. 


MILD   STEEL.  61 

Owing  to  the  comparative  slowness  of  the  working  of  a 
Siemens-Martin  charge  (which  may  occupy  about  ten  hours) 
the  Siemens-Martin  process  is  well  under  control  and  may  be 
more  deliberately  finished ;  it  has  also  been  urged  that  it  is 
not,  during  manufacture,  so  highly  oxidised  as  Bessemer  steel. 

Siemens-Martin  steel  is  in  high  repute  and  favour  in 
Britain,  while  in  the  United  States  of  America  Bessemer  steel 
is  more  abundantly  produced. 

ACID  STEEL. — Both  Bessemer  and  Siemens  processes  were 
originally  conducted  in  plant  lined  with  material  in  which 
silica  largely  predominated.  Chemically,  silica  (Si02)  is  of  an 
acid  nature  (see  p.  26),  and  only  those  pig  irons  which 
contained  small  quantities  of  phosphorus  (and  sulphur)  could 
be  converted  into  good  mild  steel  under  these  conditions. 

BASIC  STEEL. — As  most  of  the  iron  ores  at  home  and 
abroad  contain  a  notable  amount  of  phosphorus,  and  as  the 
phosphorus  is,  with  few  exceptions,  all  carried  into  the  pig 
iron  during  the  smelting  in  the  blast  furnace,  it  was  most 
desirable  that  a  workable  process  should  be  found  for  expelling 
the  phosphorus,  so  that  a  good  steel  (not  cold-short)  might  be 
obtained  from  phosphoric  pig  iron.  It  has  already  been 
explained  (see  p.  27)  that  if  phosphorus  is  to  be  got  out 
of  pig  iron,  certain  conditions  must  be  complied  with, 
including  the  presence  of  plenty  of  base.  A  basic  slag  is  neces- 
sary, and  that  slag  must,  during  the  process,  be  contained  in 
a  basic-lined  plant,  or  disastrous  results  would  follow.  (See 
p.  84  for  further  information  on  this  important  point.) 

Good  acid  steel,  whether  Bessemer-acid  or  Siemens-acid, 
is  made  from  pig  irons,  scrap,  &c.,  comparatively  low  in 
phosphorus.  Only  pure,  costly  ores  can  be  used  in  the 
manufacture  of  such  pig  irons,  and  the  supplies  are  not 
equal  to  the  fast-growing  demand  for  more  steel. 

On  the  other  hand,  good  basic  steel  may  be  made  from  pig 
iron  produced  from  cheap  and  plentiful  materials  containing 
much  phosphorus,  but  the  phosphorus  must,  during  conver- 
sion into  steel,  be  eliminated,  so  that  less  than  "05  per  cent, 
of  phosphorus  remains. 

The  pursuit  of  a  process  by  which  steel  could  be  made  from 
highly  phosphoric  materials  was  most  fascinating,  and  the 


62  IRON    AND    STEEL    MANUFACTURE. 

promised  results  were  most  important.  For  not  only  would 
the  output  of  trustworthy  steel  be  vastly  increased,  but  large 
deposits  of  iron  ores  could  then  be  utilised.  The  problem, 
and  its  importance,  were  fully  realised  in  the  latter  seventies. 
Some  of  the  best  metallurgists  in  the  chief  countries  of  the 
world  were  at  work  on  the  question.  Success  was  won  in  a 
most  unexpected  quarter.  SIDNEY  GILCHRIST  THOMAS,  who 
had  sought  relaxation  from  his  prosaic  duties  as  clerk  in  an 
East  London  police  court  by  attending  evening  classes,  solved 


Sidney  Gilchrist  Thomas. 

the  problem.*  He  was  assisted  by  his  cousin,  PERCY  CARLYLE 
GILCHRIST,  who  was  then  metallurgist  at  Blaenavun,  and  he 
had  most  kindly  encouragement  from  E.  P.  MARTIN  and  E. 
WINDSOR  RICHARDS,  who  arranged  for  trials  of  the  process 
on  a  practical  scale.  The  embodying  of  the  ideas  of  GKO.  J. 
SNELUS  and  EDWARD  RILEY  completed  the  success  of  the 
method. 

*See    the    interesting    Memoir   of  Sidney   Gilchriat    rJ  homos,    by 
R.  W.  Burnie. 


MILD    STEEL.  63 

Steel-making  flourishes  in  certain  districts  because  local 
raw  materials  have  been  made  available  by  the  working  of 
the  basic,  or  Thomas-Gilchrist,  process. 

The  great  rise  in  the  German  steel  trade  is  due  to  the 
successful  working  out  of  the  basic  process  on  a  commercial 
scale  by  the  untiring  perseverance  of  SIDNEY  GILCHRIST 
THOMAS.  America,  also,  has  profited  immensely  by  the  work 
of  the  same  genius.  Vast  ore-bearing  territories  in  the 
United  States  have  been  developed  lor  the  supply  of  ore  for 
the  manufacture  of  pig  iron,  which  is  worked  into  steel  by 
the  basic  open-hearth  system. 

Basic  steel,  corresponding  in  chemical  composition  to  acid 
iteel,  is  regularly  made. 


64 


CHAPTER  VII 

PLANT  AND  APPLIANCES  FOR  THE  ACID  BESSEMER 
PROCESS  OF  STEEL-MAKING. 

THIS  process  aims,  in  the  first  instance,  at  the  purifying  of 
melted  pig  iron  (of  selected  quality)  by  quickly  blowing  air 
through  it  in  a  vessel  called  a  converter.  At  the  hands  of 
Bessemer  the  converter  underwent  many  changes  in  design. 
At  first  he  tried  a  fixed  converter;  afterwards  he  employed 
converters  which  could  be  rotated  into  positions  which 
facilitated  the  charging  and  discharging  of  the  metal.  In 
shape,  too,  the  converter  has  been  modified.  In  the  earlier 
forms  the  upper  part  (the  hood  or  nose)  was  very  much  con- 
tracted and  sloped,  with  the  idea  of  preventing,  as  far  as 
practicable,  the  ejection  of  metal  and  slag  during  the 
"  blow." 

Improvements  were  introduced  by  Alexander  Lyman 
Holley,  of  New  York,  who  arranged  that  the  mouth  should  be 
concentric,  so  as  to  permit  of  charging  from  two  positions — a 
distinct  advantage  for  steel-making.  He  also  carried  into 
practice  the  idea  of  building  up  the  converter  of  three 
separate  parts  fixed  together  by  means  of  hinged  flaps  and 
cotter  bolts — an  arrangement  which  helps  in  the  quick 
replacement  of  rapidly-worn  parts  by  corresponding  ones 
which  have  been  lined  anew,  properly  dried,  and  got  into 
good  condition  for  work. 

The  modern  Bessemer  converter  is  a  capacious  vessel  of 
mild  steel  plates  firmly  rivetted  together  and  lined  with  a 
refractory  material  to  withstand  the  very  high  temperature, 
the  intense  chemical  action,  and  the  wear  and  tear  incidental 
to  the  work  done.  The  converter  is  somewhat  barrel-shaped. 
At  one  end  is  the  opening  through  which  it  is  charged  and 
discharged ;  at  the  other  end  are  numerous  openings  (the 
tuyere  holes)  through  which  the  strong  air-blast  is  injected. 


ACID    BESSEMER     PLANT. 


65 


Encircling  the  converter  at  its  widest  part  is  a  heavy  cast-steel 
ring,  to  which  two  trunnions  are  firmly  attached.  The 
trunnions  may  be  said  to  be  short  axles.  They  rest  on 
suitable  bearings,  and  not  only  support  the  converter  but 
serve  other  useful  purposes.  Attached  to  one  is  a  large 
toothed  wheel  which  gears  into  a  horizontal  rack.*  The  rack 


Fig.  22.— Bessemer  Converter— Part  Elevation,  part  Section. 

I, 


A,  Toothed  wheel. 

B,  Trunnion  belt. 

C,  Ganister  lining. 

D,  Iron  shell. 

E,  Brackets  for  bolts. 

F,  Pin  for  cotter  bolt. 

G,  Trunnion  belt. 
H,  Blast  pipe. 


Support   for    blast-pipe 

trunnion. 
J,    Blast-box  plate. 
K,  Blast  box. 
L,  Guard  plate  for  keeping 

tuyeres  in  position. 
M,  Tuyere. 


is,  when  required,  actuated  by  a  horizontal  double-acting 
hydraulic  ram,  and  as  the  rack  is  moved  backwards  or  for- 
wards it  causes  the  toothed  wheel  to  revolve,  and  with  it  the 
converter  to  rotate  to  any  desired  inclination  or  position. 
The  other  trunnion  forms  part  of  the  blast  pipe  through 
which  the  tremendous  air-blast  is  sent  from  the  blowing 

*  Sometimes  the  rack  is  vertical. 


66 


IRON    AND    STEEL    MANUFACTURE. 


engine  to  the  tuyere  box  (under  the  bottom  of  the  converter) 
to  be  distributed  to  the  several  tuyeres. 

The  Tuyeres,  with  the  necessary  number  and  size  of  tuyere 
holes  for  acid-lined  converters,  are  carefully  moulded,  dried, 
and  kiln-fired,  and  are  supplied  ready-made  to  most  steel- 
works. They  are  slightly  tapered  so  that  they  may  be  more 
easily  fitted  into,  and  held  fast  in,  the  openings  which  are  left 
in  the  tuyere  plug  of  the  converter  bottoms.  The  tuyeres 
are  pushed  into  the  openings,  luted  with 
moistened  fireclay  or  ganister,  and  held  firmly 
in  position  by  means  of  the  guard  plate,  which 
is  a  large  disc  with  openings  corresponding  to, 
but  a  little  smaller  than,  the  larger  end  of  each 
tuyere.  The  tuyeres  may  be  held  in  position 
by  metal  "lugs"  which  can  be  turned  round  on 
their  pivot  studs  to  permit  removal. 

In  one  works  the  18-ton  converters  have 
each  24  tuyeres,  and  each  tuyere  has  19  holes 
of  T5F  inch  diameter.  This  equals  35  square 
inches  of  tuyere  hole  area,  and  may  be  accepted 
as  fairly  representing  British  Bessemer  (acid) 
practice  in  this  particular.  The  bottom  may 
last  for  twenty  blows,  and  the  hood  and  body 
of  the  converter  may  need  relining  after  twelve 
months ;  these  figures  representing  average 
working. 


Fig.  23. 
Bessemer 
Tuyere. 


The  material  used  for  lining  the  converter  is  good  ganister, 
which  may  have  the  following  composition  : — 


Constituents. 

Chemical  Formulae. 

Percentage. 

Silica,     

Si02 

94-3 

Alumina, 
Iron  oxide, 

ALA* 
FeO 
CaO 

1-5 
1-2 

0-5 

Magnesia, 
Alkalies, 
Water,    . 

MgO 
Na.,0  and  K2O 
"  H2O 

0-2 
O'l 
2-2 

100-0 

ACID    BESSEMER     PtANT.  67 

To  line  a  vessel  with  ganister  the  three  pieces — namely, 
the  hood  or  nose,  body,  and  bottom — are  each  dealt  with 
separately.  The  rivetted  sheathing  for  the  hood  or  nose  is 
inverted  on  a  platform ;  a  wooden  core  or  plug  of  the  internal 
size  and  shape  is  placed  correctly,  and  the  space  between  the 
plug  and  the  sheathing  is  filled  and  rammed  with  crushed 
and  moistened  ganister ;  or  tar  may  be  used  as  a  binding 
material.  The  bottom  part  is  also  rammed  with  ganister, 
openings  being  left  for  the  insertion  of  the  fireclay  tuyeres. 
The  body  is  generally  lined  with  suitably  curved  silica  bricks. 
These  arc  built  within  the  rivetted  plates  which  make  up 
the  shell,  and  are  carefully  cemented  with  a  thin  slurry  of 


J 


Fig.  24. — Arrangement  for  Ramming  Converter. 

A,  Platform.  C,   Ganister  lining. 

B,  Iron  shell.  D,  Plug. 

ganister.  The  body  is  lined  while  the  shell  is  in  its  ordinary 
position ;  the  other  parts  are  rammed  in  a  separate  building 
in  the  work.  The  parts  are  placed  in  position  by  overhead 
cranes,  or  by  trolleys  carrying  hydraulic  lifting  (and  lowering) 
appliances,  and  are  fastened  by  hinged,  slotted  flaps  and 
cotter  bolts. 

The  several  parts  having  been  lined  and  bolted,  each  to  its 
adjoining  part,  live  coal  may  be  put  into  the  converter  and  a 
gentle  air  current  sent  through  it  so  as  to  thoroughly  dry  the 
lining.  The  converter  having  been  thus  dried  and  warmed,  is 
rotated  till  the  month  is  downwards  and  the  ash  and  unburnt 
fuel  fall  out.  It  is  then  ready  to  receive  the  charge. 


68  IRON    ANJ)    STEEL    MANUFACTURE. 

The  Air-blast  is  urged  by  powerful  blowing  engines  and  is 
delivered  at  a  pressure  of  25  Ibs.  per  square  inch. 

On  an  elevated  platform,  or  pulpit,  as  the  workmen  call  it, 
is  a  range  of  levers — like  those  in  a  railway  signal  box — by 
which  the  "  pulpit  man  "  controls  the  duration  of  the  blow,  the 
position  of  the  converters,  and  the  pouring  of  steel  and  slag  as 
directed  by  the  "  blower  "  who  is  in  charge. 

The  Bessemer  Ladle  enables  the  steel  free  from  slag  to  be 
poured  into  the  ingot  moulds,  even  if  steel  and  slag  have  been 
poured  into  it  from  the  converter.  These,  by  reason  of  the 
fluidity  of  each,  and  of  the  decided  difference  in  density,  soon 
separate  from  each  other ;  the  slag,  being  much  lighter,  rising 
to  the  top.  A  layer  of  slag  floating  on  the  top  of  the  steel 
protects  the  latter  from  chilling  and  from  oxidation.  Then, 
when  the  steel  is  run  out  through  the  nozzle  in  the  bottom 
of  the  ladle,  it  is — all  except  the  last  of  it  at  least — free 
from  slag. 

The  Bessemer  ladle  consists  of  a  shell  or  sheath  of  mild 
steel  plates  rivetted  together.  It  is  lined  within  with 
rammed  ganister  or  with  thin  firebricks  of  good  quality 
which  are  carefully  cemented  in  position  by  a  mortar 
of  ganister.  At  the  lowest  part  of  the  ladle  there  is  a 
space  for  receiving  the  fireclay  nozzle  through  which  the 
metal  is  poured.  Into  this  a  fireclay  stopper  at  the  end 
of  a  rigid  iron  or  steel  rod  is  carefully  adjusted.  The 
rod  is  covered  with  fireclay  sleeves,  in  short  lengths, 
which  are  fitted  to  each  other  from  the  stopper  up  to  above 
the  lip  of  the  ladle  (see  fig.  25).  These  are  all  fitted  with 
care  and  well-dried  before  being  attached  to  the  arrangement 
at  the  top  for  actuating  the  rod,  and  adjusted  to  the  nozzle  at 
the  bottom.  The  arrangement  at  the  top  may  consist  of 
cranks  worked  by  the  action  of  an  outside  rod  which  is  guided 
by  sockets  fixed  on  the  outside  of  the  ladle.  The  outside  rod 
is  moved  up  or  down,  as  required,  by  means  of  a  hand  lever 
fitted  to  a  pivot  stud.  Instead  of  the  crank  arrangement  the 
outer  rod  may  be  bent  over  so  that  the  inner  rod,  with  the 
sleeves,  &c..  can  be  attached. 

The  ladle  must  be  hot  and   the   stopper  rod  arid  nozzle 


ACID    BESSEMER    PLANT. 


69 


set  to  a  nicety  before  the  steel  is  poured  into  it.  The  ladle 
is  carried  at  the  end  of  a  platform  which  is  pivoted  at  or  near 
the  centre  so  that  it  can  be  swung  in  a  circle  from  its  point 


Fig.  25. — Teeming  Bessemer  Steel  into  Ingot  Moulds. 


A, 

0,' 

t>, 
E, 
F, 

G, 
H, 


Ladle. 
Trunnion. 
Support  for  rod. 
Sleeves  covering  iron  rod. 
Nozzle  or  outlet. 
Top  of  crane  stem  project- 
ing through  roof  support. 
Brackets  for  crane  stem. 
Stay  rod. 


I,     Hydraulic  ram. 

J,    Staging. 

K,  Piston  of  crane  stem. 

L,    Ingot  mould. 

M,  Trolley. 

N,  Arrangement  for  regulating 

the  position  of  the  trolley 

during  teeming. 
0,  Cylinder. 


under  the  converter  to  the  semi-circular  casting  pit  where  a 
set  of  ingot  moulds  have  been  placed  to  receive  the  steel 
The  nozzle  of  the  ladle  having  been  brought  ove?  the  centre 


70 


IRON    AND    STEEL    MANUFACTURE. 


of  the  first  mould  of  the  series,  the  hand  lever  is  unfastened 
and  the  free  end  is  moved  so  as  to  push  the  rod  upwards, 
thus  opening  a  passage  between  the  stopper  and  the  nozzle 
and  permitting  the  outflow  of  the  steel  into  the  ingot  mould. 
When  the  mould  is  sufficiently  filled  the  stopper  is  pressed 
down  and  the  ladle  is  swung  over  the  next  ingot  mould,  which 
in  turn  is  filled  with  the  steel.  And  so  the  "  teeming "  is 
continued  till  all  the  steel  has  been  poured.  The  ladle  is 
then  turned  over  so  that  the  slag  is  emptied  out.  The  nozzle 
is  then  knocked  out  and  a  new  one  fitted  in, 
to  which,  in  due  course,  a  covered  stopper 
rod  will  be  carefully  set. 

Instead  of  the  ladle  being  swung  over  each 
individual  mould,  it  is  not  an  unusual  arrange- 
ment to  have  the  moulds  mounted  on  low 
trolleys  (see  fig.  25)  and  to  push  the  trolleys 
one  by  one  up  to  the  pointer  which  regu- 
lates the  position  under  the  ladle.  The 
"  teeming "  from  the  ladle  is  regulated  by 
the  stopper  as  described  above. 

Ingot  Moulds  are  strong  hematite-iron 
castings  with  wrought-iron  or  steel  lugs  at 
the  upper  end,  as  shown  in  fig.  26.  They 
are  usually  open  both  at  top  and  bottom,* 
and  they  are  broader  at  the  bottom  than  at 
the  top  so  that  they  may  be  more  easily 
stripped  from  the  steel  ingot  when  the  latter 
is  cool  enough.  Stripping  is  performed  by  inserting  in  the 
lugs  hooks  attached  to  a  chain  which  is  moved  by  a  crane, 
as  shown  in  fig.  51,  p.  120. 

The  Bessemer  Crane,  for  lifting  and  conveying  ingots, 
moulds,  &c.,  is  worked  on  the  hydraulic  system,  and  is  in 
principle  similar  to  the  hydraulic  ram,  &c.,  shown  in  fig.  25. 
It  consists  essentially  of  a  strong  hydraulic  cylinder  in  which 
a  long  upright  stem  works  smoothly  without  being  too  loose. 
The  stem  sometimes  extends  to  the  roof  by  which  it  is  braced  ; 

*  The  moulds  are  set  on  heavy  cast-iron  slabs  before  "teeming"  the 
steel  into  them. 


Fig.  26.— Ingot 
Mould. 


ACID    BESSEMER    PLANT.  71 

if  not,  a  counterpoise  is  fitted  to  another  arm  corresponding 
to  the  jib.  From  the  stem  there  projects  an  arm  or  jib  along 
which  a  little  trolley  runs  easily.  From  a  hook  attached  to 
the  trolley  the  ingot  or  mould  to  be  moved  is  suspended. 
By  admitting  water  under  the  bottom  of  the  stem  the  stem 
may  be  raised,  lifting  with  it  the  weight,  be  it  ingot  or 
mould,  which  can  then  be  swung  round  and  run  along  the  jib. 
Then  on  allowing  the  water  to  escape  from  the  cylinder  the 
suspended  article  can  be  lowered. 

There  are  other  kinds  of  cranes  in  extensive  use  in  steel 
works.  Hydraulic  and  electric  arrangements  for  stripping 
the  moulds  from  off  the  ingots  are  also  used. 

The  fluid  metal  required  for  the  Bessemer  process  may  be 
obtained  by  remelting  the  pig  iron  in  a  cupola,  or  by  conveying 
in  a  ladle  the  molten  pig  iron,*  in  the  condition  in  which  it 
comes  from  the  blast  furnace,  direct  to  the  converter. 

There  is  a  newer  and  a  better  method — namely,  that  of 
conveying  the  pig  iron  as  it  runs  from  the  blast  furnace  into 
a  metal  mixer — which  may  be  described  as  a  cistern — and 
taking  off  from  the  mixer,  in  such  quantities  and  at  such 
times  as  needed,  the  fluid  metal  for  use  in  the  converter. 
Storing  in  a  mixer  tends  to  yield  a  more  uniform  quality  of 
metal  throughout  the  working  week. 

A  cupola  is  a  shaft  furnace  open  at  the  top.  It  is  of  mild 
steel  plates  rivetted  together,  and  is  lined  with  firebricks  set  in 
a  grouting  or  mortar  of  fireclay.  A  working  bottom  is  made 
by  ramming  sand  or  ganister  into  the  required  shape. 

Near  the  top  is  a  platform  and  an  opening  for  charging. 
On  one  side,  near  the  bottom,  is  an  openingf  by  which  the 
slag  and  unburnt  coke  may  be  drawn  when  the  cupola  has 
ceased  work ;  it  is  also  useful  for  repairs,  for  making  up  the 
sand  bottom,  and  for  putting  in  the  coke  and  the  kindling 
material  when  beginning  or  resuming  work. 

When  a  cupola  is  in  working  order,  pig  iron  and  coke  are 

*  As  a  matter  of  convenience,  we  consider  the  "metal"  which  is 
tapped  from  an  iron-smelting  blast  furnace  to  be  pig  iron  whether  it  is 
formed  into  "  pigs  "  or  not.  With  regard  to  "  pigs  "  see  p.  208. 

fThis  opening  is  closed,  and  is  covered  with  an  iron  plate  during  the 
melting  of  the  charge. 


C,  Air  or  blast  belt. 

D,  Charging  platform. 

E,  Charging  door. 

F,  Iron  shell. 


G,   Angle  iron  for  supporting 
bricks. 


Fig.  27.— Steel  Work  Cupola— Half  Elevation,  Half  Section. 

A,  Slag  spout. 

B,  Blast  pipe  from  blower. 

H,  Firebrick  lining. 

J,  Tuyere. 

K,  Taphole. 

L,  Spout  or  lander  for  melted 


metal 


ACID    BESSEMER    PLANT. 


73 


charged  in,  along  with  a  little  limestone.  An  air-blast  is 
forced  in  through  tuyeres,  which  may  be  in  one  row  or  more. 
The  burning  of  the  coke  raises  the  temperature,  and  melts  the 


pig  iron  and  the  slag  which  is  formed.      These  descend,  and 
are  taken  off  through  their  respective  tapholes. 


74  IRON    AND    STEEL    MANUFACTURE. 

During  the  descent  a  little  loss  occurs  through  oxidation  of 
iron,  manganese,  and  silicon,  and  the  "metal"  takes  up  a 
small  amount  of  sulphur  from  the  fuel. 

The  cupola  shown  in  lig.  27  is  of  the  following 
dimensions : — 

Height  to  charging  platform,  .  .         .22  feet. 

Internal  diameter  at  widest  part,  .  8     „ 

„  middle     „  5     „ 

„  „         „  lower       „  6     „ 

There  arc  seven  tuyeres,  each  5  inches  diameter,  set  4  feet 
6  inches  above  the  floor  level,  and  the  blast  is  supplied  at  a 
pressure  of  about  If  Ibs.  per  square  inch.  The  slaghole  is 
3  inches  below  the  tuyeres. 

Such  a  cupola  melts  500  tons  of  pig  iron  in  24  hours,  and 
requires  repairs  to  its  lining  after  working  about  60  hours. 

When  needed,  the  melted  pig  iron  is  tapped  from  the 
cupola  into  a  ladle  of  the  kind  shown  in  fig.  28,  which 
conveys  it  to  the  Bessemer  gantry — that  is,  the  platform  at 
the  converters — and  by  a  side  lip  it  is  poured  into  the 
converter. 


75 


CHAPTER  VIII. 
THE  ACID  BESSEMER  PROCESS. 

BY  the  successful  working  of  this  process,  suitable  molten  pig 
iron  is  purified  and  converted  into  either  medium  or  mild 
steel  by  the  action  of  a  rapid  current  of  air  which  is  forced 
through  it.  This  causes  the  oxidation,  or  burning,  of  certain 
elements,  which  are  thereby  removed  from  the  pig  iron.  The 
"blown  metal"  is  then  finished  by  the  judicious  addition  of 
hot  spiegel-eisen  or  ferro-manganese.  The  steel  is  then  poured 


Fig.  29.— Pouring  "Metal"  into  a  Converter. 

from  the  converter  into  a  ladle,  from  which  it  is  tapped  into 
ingot  moulds.  The  steel  ingots  are  afterwards  rolled  into  the 
shapes  required — such  as  plates,  angles,  girders,  bars,  springs, 
tyres,  axles,  &c. 

Working   an   Acid   Bessemer  Blow, — The  Bessemer  con- 
verter, lined   as    described    in    the    previous    chapter,  being 


76 


IRON    AND    STEEL    MANUFACTURE. 


in  good  condition  and  hot,  is  rotated  till  it  is  nearly 
horizontal.  The  position  must  be  such  that  the  melted  metal 
cannot  flow  into  the  holes  of  the  tuyeres.  The  charge  of 


Fig.  30.— Bessemer  Converter  while  Blowing. 


Fig.  31.— Pouring  Steel  from  Converter. 


THE    ACID    BESSEMER    FROCESSl 


77 


fluid  pig  iron  is  run  into  the  converter*  from  the  ladle  which 
conveyed  it,  and,  if  too  hot,  scrap  steel  is  thrown  in.  An 
alarm — a  loud  whistle  from  a  jet — is  sounded,  so  as  to  warn 
the  workmen  to  get  out  of  the  way  of  the  flame  and  sparks 
which  are  ejected  when  the  blast  is  turned  on.  The  vessel 
is  then  rotated  till  nearly  vertical,  the  blast  being  continued 
until  it  is  judged  that  the  silicon  and  carbon  have  been 
oxidised — a  point  indicated  by  a  change  in  the  sound  of  the 
blow  and  by  the  difference  in  the  flame  when  it  "drops." 
The  alarm  is  again  heard,  and  the  converter 
is  turned  down  to  a  safe  horizontal  position. 
The  converter  then  contains  metal  and  slag. 
By  reason  of  its  much  lower  density,  the  slag 
soon  separates  by  rising  to  the  surface.  The 
metal  at  this  stage  is  highly  oxygenated. 
Addition  of  a  weighed  quantity  of  hot  ferro- 
manganese  or  spiegel-eisen  soon  deoxidises  the 
metal,  and  converts  it  into  mild,  medium,  or 
hard  steel  by  giving  to  it  the  desired  percen- 
tage of  carbon.  All  being  ready,  the  steel  is 
poured  into  a  Bessemer  ladle,  and  from  thence 
it  is  teemed  into  the  ingot  moulds. 

When  the  steel  ingot  has  become  cold  enough 
to  safely  bear  removal,  the  mould  is  stripped 
off  (as  shown  in  fig.  51),  and  the  ingot  is 
gripped  by  "dogs"  on  the  end  of  a  chain, 
hoisted  by  a  crane,  and  conveyed  to  be  re- 
heated or  stocked.  The  weight  of  the  ingot 
tends  to  pull  the  dogs,  and  the  grip  is  thereby 
tightened.  The  ingot  is  thus  firmly  held 
until  released  when  it  ceases  to  be  suspended. 

The  further  treatment  of  steel  ingots  is  dealt 
with  in  Chapter  xiii. 


Fig.  32.  — Steel 
Ingot  and 
Dogs. 


The  Principles  of  the  Bessemer  Process  may  be  gathered 
from  a  study  of  the  appended  table  of  composition,  and  a 
consideration  of  the  chemical  changes  which  take  place  during 
the  course  of  conversion  into  mild  steel : — 


historic  reasons  the  old-fashioned  type  of  hood  is  shown. 


78 


IRON    AND    STEEL    MANUFACTURE. 


JMtM  Steel 

Constituents. 

Chemical 
Symbols. 

Hematite 
Pig  Iron 
before  Blowing. 

Hematite 
Pig  Iron 
after  Blowing. 

Produced 
after  Addition 
of  Ferro- 

M  auganese. 

Graphitic  carbon, 

c 

3-42 

None 

None 

Combined  carbon, 

c 

0-46 

Trace 

0-20* 

Silicon, 

Si 

2-20 

None 

0-02 

Phosphorus, 

P 

0-045 

0-048 

0-05 

Sulphur, 

s 

0-045 

0-048 

0-04S 

Manganese,  . 

Mn 

0-47 

Trace 

0-50 

Oxide  of  iron, 

None    J 

Present,  but 
not  estimated. 

|     None 

Iron,     . 

Fe 

A 

A 

A 

Total,  . 

100-000 

100-000 

100-000 

Chemical  Considerations. — The  force  and  volume  of  the 
powerful  air-blast,  which  is  urged  by  the  blowing  engine  at 
high  pressure  into  the  tuyeres,  can  support  the  heavy  mass 
of  metal,  and  keep  it  dancing,  as  it  were,  on  a  cushion  of 
air,  so  that  it  cannot  run  down  and  choke  the  tuyere  holes. 
The  air  finds  its  way  up  through  the  mass  of  hot,  fluid 
metal ;  there  is  a  violent  commotion  and  sharp  chemical 
action.  Even  in  that  brief  passage  the  oxygen  of  the  air 
exerts  its  chemical  power  with  much  effect.  Fortunately,  it 
is  selective  in  its  action. 

For,  as  in  the  puddling  process,  one  metalloid  is  attacked 
by  oxygen  in  preference  to  another,  so  is  it  in  the  Bessemer 
process.  Generally  the  silicon  is  first  attacked  ;  nearly  at  the 
same  rate  the  carbon  is  also  attacked.  The  manganese  in  due 
course  is  also  oxidised,  so  that  at  the  time  the  flame  "  drops  " 
these  three  elements  are  all  practically  absent.  Considering 
the  large  quantity  of  iron  present  the  oxidation  of  that  metal 
is  small.  It  is  more  than  probable  that  the  resulting  oxides 
of  iron  assist  in  the  rapid  oxidation  of  other  elements. 

There  is  no  elimination  of  phosphorus  or  of  sulphur,  and, 
as  the  quantity  of  these  elements  originally  present  is,  at  the 
end,  concentrated  in  a  smaller  weight  of  metal,  the  percentage 
of  each  of  these  elements  is  higher.  The  percentage  increase 
is  slight  but  is  important. 

*  The  percentage  of  carbon  is  easily  adjusted  so  as  to  suit  the  purpose 
for  which  the  steel  is  made, 


THE    ACID    BESSEMER    PROCESS.  79 

The  chemical  reactions  involved  may  briefly  be  explained 
thus  : — 

(a)  Carbon  (C)  is  oxidised,  partly  into   carbon  monoxide 

(CO)  and  partly  into  carbon  dioxide  (C02),  and  the 
changes  may  be  concisely  indicated  by  chemical 
symbols : — 

C  +         0,  COo 

Carbon    and     oxygen    yield       carbon  dioxide. 

2C  +          0,  2CO 

Carbon    and    oxygen    yield     carbon  monoxide. 

The  gases,  carbon  monoxide  and  carbon  dioxide, 
escape  into  the  air. 

(b)  Silicon   (Si)  is  oxidised  into  silica   (Si09) — a  reaction 

noted  in  the  chemical  equation : — 

Si  +  02  Si02 

Silicon       and       oxygen       yield      silica. 

Silica  forms  the  chief  component  of  the  slag. 

(c)  Manganese  (Mn)  is  oxidised  to  manganous  oxide  (MnO), 

as  symbolised  in  the  following  equation  : — 

2Mn  +  0.,  2MuO 

Manganese    and     oxygen     yield     manganous  oxide. 

The  manganous  oxide  goes  into  the  slag. 

(d)  The  iron  which  suffers  oxidation  is  changed  partly  into 

ferrous  oxide  (FeO)  and  ferric  oxide  (Fe203) — changes 
represented  in  chemical  symbols  thus — 

2Fe       +          02  2FeO 

Iron     and     oxygen    yield    ferrous  oxide. 

4Fe       +         302       .  =  2FeA 

Iron    and    oxygen    yield*   ferric  oxide. 

These  oxides  find  their  way  into  the  slag. 

Oxidation  and  Deoxidation  of  Bessemer  Metal.— A  belief  is 
current  that  a  lower  oxide  of  iron  exists,  and  that  the  lower 


80 


IRON    AND    STEEL    MANUFACTURE. 


oxide  clings  to  the  melted  iron  and  causes  that  condition 
which  makes  ordinary  blown  Bessemer  metal  worthless.  The 
existence  of  that  lower  oxide  has  not  been  proved.  There 
is  also  a  belief  that  oxygen  is  dissolved  in  blown  Bessemer 
metal.  In  either  case  the  mischievous  oxygen  is  removed  by 
the  addition  of  hot  manganese  which  takes  over  the  oxygen 
from  the  iron  and  becomes  converted  into  oxide  of  manganese, 
which  is  quickly  carried  into  the  slag. 

In  the  absence  of  definite  information  concerning  the  com- 
position of  the  supposed  lower  oxide  of  iron,  the  chemical 
change  by  which  deoxidation  is  effected  may  be  represented 
thus — 

FeO  +  Mn  MnO  +        Fe 

Iron  oxide    and    manganese    yield    manganous  oxide    and    iron. 

The  following  table  shows  the  composition  of  certain 
grades  of  the  "  triple  compounds  of  manganese,  carbon,  and 
iron  "  used  in  the  manufacture  of  Bessemer  and  other  steels. 


Constituents 

Chemical 
Symbols. 

Spiegel- 
eisen. 

Medium 

Ferro- 
Manganese. 

High  Grade 
Ferro- 
Manganese. 

Manganese, 

Mn 

15-12 

53-36 

79-85 

Carbon  (combined),      . 

C 

4-43 

6-12 

6-64 

Silicon, 

Si 

0-47 

0-46 

0-71 

Sulphur, 

S 

0-02 

0-01 

o-oi 

Phosphorus, 

P 

0-23 

0-11 

0-20 

Iron,    .... 

Fe 

A 

A 

A 

100-00 

100-00 

100-00 

For  additional  analyses  see  p.  237. 

Spiegel-eisen  is  generally  known  in  works  as  "spiegel"; 
ferro-manganese  is  known  as  "  ferro  "  or  "  manganese."  All 
such  materials  are  known  in  works  by  the  common  name 
of  "physic." 


THE    ACID    BESSEMER    PROCESS.  81 

In  the  Bessemer  process  the  functions  of  these  materials 
are  threefold. 

(a)  To  "  restore  the  nature  "  of  the  metal  by  removing  the 

combined  or  dissolved  oxygen. 

(b)  To  add  the  necessary  amount  of  carbon  required  in  the 

steel  to  suit  its  intended  purpose. 

(c)  To  add  a  certain  amount  of  manganese  to  the  finished 

steel — in  which  it  acts  to  some  slight  extent  as  a 
"  corrective  "  to  the  phosphorus,  and  more  especially 
to  the  sulphur  which  is  always  present. 

Recarburising. — The  quantity  and  kind  of  material  added 
are  determined  by  the  percentage  of  carbon  required  in  the 
finished  steel.  Thus,  if  a  mild  steel  (that  is,  one  low  in 
carbon)  is  ordered,  ferro-manganese  is  used ;  if  a  steel  con- 
taining a  higher  percentage  of  carbon  is  wanted,  spiegel-eisen 
is  used.  Why  this  is  so  is  explained  in  Chapter  xxiii. 

Coke  and  other  substances  rich  in  carbon  are  occasionally 
used  for  recarburising. 

The  ferro-manganese  is  broken  into  little  lumps  (say  about 
4  inch  cubes  or  even  smaller  pieces),  and  is  usually  red  hot 
when  charged  into  the  molten  metal  in  the  converter.  It 
soon  melts,  and  time  is  allowed  for  its  diffusion  through 
the  "  metal."  When  spiegel-eisen  is  used  it  is  charged  into 
the  converter  in  the  fluid  condition,  as  such  a  large  quantity 
would,  with  difficulty  and  uncertainty,  melt  in  the  metal  in 
the  converter. 

If  the  blow  is  stopped  before  all  the  carbon  is  burned  out, 
less  recarburising  material  will  of  course  be  needed.  Swedish 
Bessemer  practice  is  interesting  in  this  particular.  Carbon 
may  be  added  directly  to  the  metal  at  the  end  of  a  blow,  or 
grey  hematite  pig  iron  may  to  some  extent  be  used.  Other 
materials  for  promoting  soundness  in  steel  contain  aluminium 
or  silicon  in  notable  proportions. 

Heat  evolved  during  a  Bessemer  Blow.— The  molten  pig 
iron  which  is  run  into  the  converter  is  red  hot,  and,  although 

6 


82  IRON   AND    STEEL    MANUFACTURE. 

a  large  volume  of  ordinary  cold  air  is  forced  through  it,  the 
metal  is  much  hotter  at  the  end  of  the  blow.  The  decided 
rise  in  temperature  is  due  to  the  rapid  burning  of  the  carbon, 
the  manganese,  some  of  the  iron,  and  especially  the  burning 
of  the  silicon.  Much  of  the  heat  evolved  by  the  oxidation  of 
the  carbon  is  carried  quickly  away  in  the  gases  which  escape 
by  the  mouth  of  the  converter,  whereas  the  silica  resulting 
from  the  oxidation  of  the  silicon  remains  in  the  converter  (as 
a  component  of  the  slag)  until  it  is  poured  off  after  the  end  of 
the  blow.  The  silica,  it  may  be  well  to  explain,  unites 
chemically  with  oxide  of  iron  and  other  bases,  forming  at  the 
high  temperature  attained  during  a  "  blow  "  a  slag  so  very 
fluid  that  it  can  contain  a  considerable  quantity  of  chemically 
free  silica  and  yet  remain  fluid. 

The  British  Bessemer  blower  mainly  relies  on  the  percentage 
of  silicon  for  the  maintenance  of  the  heat  needed  to  keep 
his  metal  in  the  condition  6f  fluidity  required. 

When  the  metal  is  too  hot  at  the  finish  it  is  apt  to  be 
"  wild  "  in  the  moulds  and  to  produce  unsound  ingots.  On 
the  other  hand,  metal  which  is  too  cold  is  apt  to  lead  to  an 
insufficient  intermingling  of  the  ferro-manganese  or  spiegel- 
eisen ;  there  is  also  a  serious  risk  of  steel  solidifying  in  the 
ladle  and  forming  a  "  skull,"  of  the  teeming  not  being  smooth, 
and  the  ingots  being  unsatisfactory. 

The  best  cure  for  cold  blows  is  hotter  and  more  highly 
siliceous  pig  iron.  If  a  supply  of  such  cannot  be  had  a 
greater  volume  of  blast  through  wider  tuyeres  should  be 
arranged  for. 

For  blows  which  finish  too  hot,  quite  the  contrary  con- 
ditions should  be  set  up,  and  a  plentiful  supply  of  suitable 
scrap  steel,  which  should  be  liberally  thrown  into  the  con- 
verter before  running  in  the  melted  pig  iron,  would  go  far  to 
remedy  matters. 


THE    ACID    BESSEMER    PROCESS. 


83 


Bessemer  Slag  from  the  blowing  of  ordinary  Hematite  Fig 
Iron  may  contain  the  following  components  in  the  percentages 
stated : — 


Constituents. 

Chemical  Formulae. 

Percentage. 

Ferrous  oxide, 
Ferric  oxide,  . 
Oxide  of  manganese, 
Silica,     . 
Alumina, 

FeO 

FeA 

MnO 

Si02 

10-4 
0-5 
14-4 
69-8 
2-9 
1*7 

Magnesia,       .... 

MgO 

0-3 

100-0 

Although  slag  of  this  composition  contains  8' 3 4  per  cent, 
of  iron  and  1 T15  per  cent,  of  manganese — each  in  an  oxidised 
state — no  profitable  method  of  extracting  these  metals  has 
yet  been  devised,  and  the  slag  is  thrown  down  as  worthless 
on  slag  heaps. 

The  percentage  of  oxide  of  manganese  (MnO)  given  in  the 
above  analysis  is  much  lower  than  that  stated  in  many  text 
books,  but  it  accurately  represents  present  day  practice. 


CHAPTER   IX. 
THE  BASIC  BESSEMER  PROCESS. 

THE  intention  of  the  basic  Bessemer  process  is  to  produce 
good  malleable  metal  (mild  steel)  from  pig  iron  containing 
much  phosphorus. 

In  the  ordinary  (acid)  Bessemer  process  all  the  phosphorus 
in  the  pig  iron  is  concentrated  in  the  steel  which  is  made 
from  it.  Presence  of  more  than  0'05  per  cent,  (that  is,  equal 
to  5  in  10,000  parts)  of  phosphorus  in  steel  makes  it  "cold 
short "  and  therefore  useless  for  some  purposes  for  which  steel 
is  used.  Clearly,  then,  if  good,  reliable  steel  is  to  be  made 
from  pig  iron  containing  a  high  percentage  of  phosphorus 
some  means  must  be  found  for  eliminating  phosphorus  from 
the  metal. 

The  conditions  for  dephosphorising  pig  iron  are : — 

(a)  Fluid  metal,  and,  when  formed,  fluid  slag. 
(5)  An  active  oxidising  atmosphere. 

(c)  Intimate  intermixture  of  metal  and  slag  during  working. 

(d)  Abundance   of  suitable  base  to    hold  the  phosphorus 

which  is  liberated  from  the  pig  iron.      [Phosphorus 
when  liberated  is  oxidised  and  forms  phosphoric  acid 

WV-] 

(e)  The    presence   of    abundance   of    highly    heated    base 

necessitates  a  basic  lining  for  the  chamber  in  which 
the  operation  is  conducted. 

Because  basic  Bessemer  slag  contains  all  the  phosphorus 
from  the  pig  iron  the  slag  has  a  high  commercial  value. 

The  chief  difference  in  the  basic  Bessemer  plant,  as 
contrasted  with  the  acid  Bessemer  plant,  is  the  lining  of 
the  converter  for  the  former  with  basic  material.  And 
as  a  much  greater  bulk  of  slag  results  from  the  basic  pro- 


THE    BASIC   BESSEMER    PROCESS. 


85 


cess,  the  converter,  for  a  given  amount  of  metal,  must  be 
larger. 

The  cupolas  and  ladles  are  the  same  in  size  and  in  lining 
as  for  the  acid  process,  and  the  blowing  engines,  cranes,  ingot 
moulds,  &c.,  are  also  the  same.  They  are  described  in 
Chapter  vii. 

For  the  manufacture  of  basic  steel,  machinery  and  appli- 
ances are  required  for  making  basic  bricks  and  for  preparing 
the  basic  linings.  Machinery  for  grinding  the  slag  from  the 
basic  process  is  also  required  unless  the  slag  is  sold  in  its 
rough  state  to  merchants. 

Materials  for  Lining. — The  basic  Bessemer  converter  is 
generally  lined  with  a  prepared  mixture  of  ground  calcined 
dolomite  and  special  tar  free  from  water. 

When  limestone,  which  contains  calcic  carbonate  (CaCO3  or 
CaO,  C02 ),  is  calcined,  or,  as  the  works'  phrase  goes,  "  burnt," 
the  carbon  dioxide  is  liberated,  and  lime  (or  quicklime)  is  left. 
Lime  mixed  with  tar  would  make  a  tolerably  good  basic 
lining,  but  magnesia — which  is  left  on  strongly  calcining 
magnesite  or  magnesic  carbonate — is  a  better  substance.  It 
is,  however,  much  more  costly.  Fortunately  there  exist 
large  accessible  deposits  of  dolomite*  (or  magnesian  lime- 
stone), which  is  a  compound  carbonate  of  lime  and  magnesia. 
Prepared  dolomite  is  freely  used  as  the  material  for  lining  the 
basic  converter.  Where  magnesite  is  plentiful  and  cheap, 
magnesia  is  used.  In  Russia,  chrome  iron  ore  is  used  and  a 
lining  of  that  substance  lasts  a  very  long  time. 

COMPOSITION  OF  BASIC  REFRACTORY  MATERIALS. 


Chief  Constituents. 

Chemical 
Formulae. 

Calcined 
Limestone. 

Calcined 
Magnesite. 

Calcined 
Dolomite. 

Lime,  .... 
Magnesia,    . 
Alumina, 
Silica, 

CaO 
MgO 
A1A 
Si02 

95'7 
1-2 
0-9 
1-9 

1-8 
94'4 
2-3 
0-6 

59-5 
33-1 
2-8 
3-7 

99-7 

99-1 

99/1 

Named  after  Dolomieu,  a  famous  French  geologist. 


86  IRON   AND   STEEL    MANUFACTURE. 

These  are  derived  from — 


Chief  Constituents. 

Chemical 
Formulae. 

Limestone.* 

Magnesite.* 

Dolomite.* 

Carbonic  acid  and  other) 
volatile  matters,  .  / 

C02,  fto. 

42-7 

51-2 

46-3 

Lime,  .... 

CaO 

54-8 

0-9 

31-9 

Magnesia,    . 

MgO 

0-5 

46-3 

17'8 

Alumina, 

ALA 

0-5 

1-1 

1-5 

Silica,. 

Si62 

1-2 

0'3 

2-1 

99-7 

99-8 

99-6 

Preparation  of  the  Materials  for  Lining. — The  dolomite,  in 
lumps  as  quarried,  or  broken  into  smaller  pieces,  is  calcined  by 
being  placed  in  a  kiln,  along  with  the  necessary  fuel,  which, 
when  burning,  expels  the  carbon  dioxide.  The  calcined 
dolomite — which  shrinks  very  much  during  the  "burning" — 
is  ground  in  a  pan  mill,  and  enough  hot  anhydrous  f  tar  (or 
pitch)  to  make  a  mass  of  the  proper  consistency  is  added,  and 
thoroughly  mixed  with  it  in  the  pan  mill.  About  8  per  cent., 
by  weight,  of  the  water-free  tar  may  be  needed.  The  tar  acts 
as  a  binding  material,  and  protects,  to  some  extent  at  least, 
the  lime,  which  would  otherwise  quickly  take  up  moisture 
from  the  air. 

The  mixture  of  calcined  and  ground  dolomite  and  water-free 
tar  (or  pitch)  is  known  in  the  works  as  basic  material — a 
term  sometimes  applied  to  the  burnt  dolomite  without  the  tar 
addition.  It  may  be  used  in  the  form  of  bricks,  or  may  be 
hand-pressed  by  hot  rammers. 

To  make  basic  bricks  a  press  is  employed.  The  press  has 
a  table  which  can  be  rotated  about  its  centre.  The  table 
carries  three  moulding  boxes,  which  are  arranged  at  equal 
distances  from  the  centre  and  from  each  other.  Each  box  in 
turn  is  filled  with  the  basic  material,  a  strong  iron  plate  is 
placed  over  it,  and  the  table  is  moved  until  a  box  is  right 
under  the  hydraulic  ram,  which  descends  and  presses  the  basic 

*  These  are  not  basic  until  calcined, 
f  Anhydrous  means  "free  from  water." 


THE    BASIC    BESSEMER    PROCESS.  87 

material  until  it  half  fills  the  box.  The  table  is  moved  again 
till  the  first  box  is  over  another  but  less  powerful  ram;  the 
ram,  on  rising,  lifts  the  pressed  brick,  which  is  moved  by  hand 
and  carried  to  a  warm  place.  Meanwhile,  the  other  boxes 
have  been  filled,  and  the  second  one  has  been  under  the  press. 
And  so  the  succession  is  kept  up,  three  bricks  being  on 
the  way  at  one  time.  The  bricks,  having  been  kept  in  a 
warm  place  for  some  days,  may  then  be  packed  in  a  kiln 
and  kept  at  a  high  temperature  for  a  few  days,  or  they  may, 
while  in  the  green  state,  be  built  into  position  in  the 
converter. 

Lining  the  Basic  Converter. — The  converter  is  of  three 
parts— the  hood  or  nose,  the  body,  and  the  bottom. 

The  body  is  generally  lined  with  basic  bricks,  made  as 
previously  described,  and  set  in  plenty  of  basic  material. 
The  hood,  being  the  part  least  subjected  to  severe  usage,  is 
often  lined  with  a  mixture  made  from  clean  portions  of  old 
lining  ground  fine  and  mixed  with  more  anhydrous  tar. 
When  in  need  of  renewal  the  hood  is  turned  upside  down 
on  a  platform,  and  detached  by  undoing  the  cotter  bolts. 
It  is  then  taken  to  that  part  of  the  works — popularly  called 
the  plug  shop — where  relining  is  done.  The  old  lining  is 
removed,  and  a  core  or  pattern  is  placed  in  position. 
Kammers — long  iron  bars  with  flattened  enlargements  "at  one 
end — are  made  hot  at  the  broad  end.  Some  of  the  mixture 
is  thrown  in  between  the  shell  and  the  core,  and  workmen 
press  firmly  the  hot  rammers  on  it,  and  cause  it  to  cohere. 
More  of  the  mixture  is  supplied  and  similarly  pressed,  relays 
of  hot  rammers  being  supplied  to  the  men. 

The  bottom  is  similarly  rammed,  but  in  two  parts.  In  the 
first  place,  a  "  plug"  is  prepared,  and,  secondly,  the  plug  is 
fixed  in  the  centre  of  a  converter  bottom.  To  prepare  the 
plug,  an  iron  plate  or  disc,  surrounded  by  an  iron  cylinder,  is 
provided.  Round,  tapered  iron  rods  about  21  inches  long,  of 
the  number  and  diameter  of  the  intended  tuyere  holes,  are 
fixed  to  the  plate  (see  fig.  33).  Between  these  upright  rods  a 
small  quantity  of  ground  burnt  dolomite,  mixed  with  melted 
anhydrous  tar,  is  thrown  in,  and  carefully  pressed  with  hot 
iron  rammers  of  a  special  shape.  More  of  the  mixture  is 


88 


IRON    AND    STEEL    MANUFACTURE. 


emptied  in,  and  cemented  to  the  previous  portion  by  means 
of  the  hot  irons.  In  this  manner,  little  by  little,  the  plug  is 
built  up,  generally  to  a  thickness  of  about  1 8  inches.  When 
completed,  the  plug  is  lifted  up  on  the  iron  bottom  plate  and 
the  upright  iron  rods  are  each  struck  a  smart  blow.  As  they 
are  slightly  tapered  they  are  easily  caused  to  fall,  and  each 
leaves  a  vacant  space  for  a  tuyere  hole.  The  plug,  contained 
in  the  metal  cylinder,  is  then  carefully  dried  and  kiln-fired. 
It  is  then  set  in  the  centre  of  the  space  enclosed  by  the  iron 
work  which  constitutes  the  sheathing  of  the  "  bottom,"  and 
the  space  between  the  sheath  and  the  plug  is  filled  in  with 
basic  material,  which  is  cemented  by  ramming  in  the 
usual  way. 

The  size  and  number  of  the  tuyere  holes  vary  in  different 
works,  but  70  openings,  each  f  inch  diameter — giving  an  area 


Fig.  33.— Plate,  Cylinder,  and  Rods  for  Basic  Plug. 

of  31  inches — may  be  accepted  as  a  fair  average  for  a  15-ton 
basic  converter. 

The  plug,  as  a  whole,  may  be  rammed  by  hydraulic  pressure 
instead  of  by  hand.  At  the  North-Eastern  Works,  Middles- 
brough, this  is  regularly  done,  and  with  most  advantageous 
results.  In  some  works  fireclay  tuyeres — same  as  for  the  acid 
Bessemer  process — are  used.  They  soon  become  worn,  but 
are  easily  replaced  by  pushing  them  into  a  setting  of  basic 
material  in  the  tuyere  openings  of  the  plug. 

A  plug  lasts,  as  a  rule,  about  17  blows;  the  body  needs 
relining  after  about  120  blows;  and  the  nose  may  stand  from 
50  to  300  blows  before  requiring  relining. 


ft-    i- 

C/D        , 

O 


<u 

>«  'So 

h     o 


u    w     o         PQ     o 
<          <-•  .    *^ 


u  3 


THE   BASIC   BESSEMER   PROCESS.  89 

The  three  parts  of  the  converter  are  fixed  to  each  other 
by  means  of  cotter  bolts,  a  junction  of  basic  material  in  a 
plastic  condition  being  placed  between  each  before  pressing 
the  parts  together  prior  to  fixing. 

A  fire  is  kindled  and  kept  going  in  the  converter  till  it  is  hot. 

The  regular  supply  of  fairly  uniform  "metal"  to  the 
converters  conduces  to  smooth  working  and  helps  in  the 
production  of  steel  of  uniform  quality.  As  in  the  acid 
process,  the  pig  iron  may  be  , re-melted  in  cupolas,  or  the 
"  metal "  as  tapped  from  the  blast  furnace  may  be  taken 
directly  to  the  converter,  or  it  may  be  supplied  through  a  mixer. 

Many  mixers  are  shaped  like  open-hearth  tilting  furnaces, 
and  have  gas  producers  and  regenerators.  In  some  instances 
a  considerable  diminution  in  the  percentage  of  silicon  and  of 
sulphur  takes  place  in  the  mixer.  Scrap  steel  can  be  melted 
in  the  mixer  and  "metal"  sufficiently  hot  for  comfortable 
flowing  may  be  delivered  as  required. 

Mechanical  contrivances  which  facilitate  the  conveyance  of 
metal  are  advantageously  adopted.  The  more  rapid  pro- 
duction resulting  from  their  adoption  more  than  compensates 
for  the  cost  of  installing  and  working.  Fig.  34  shows  a 
double-bugey  ladle  crane  of  the  substantial  type  made  by 
Messrs.  Thomas  Broadbent  and  Sons,  Huddersfield.  This 
crane  is  fitted  with  five  electric  motors.  The  illustration 
shows  the  molten  metal  being  poured  into  a  converter,  the 
rear  chain  and  pulley  being  brought  into  action  to  tilt  the  ladle. 

Working  a  Basic  Bessemer  Blow. — When  a  basic-lin^d 
converter  is  in  good  working  condition,  and  hot,  it  is  turned 
with  its  mouth  towards  the  upper  gantry,  from  which  a 
quantity  of  calcined  or  "burnt"  lime  is  shot  into  it  (see 
fig.  35  on  next  page).  The  converter  is  then  rotated  until  it 
is  in  a  proper  position  to  receive  the  charge  of  melted  basic 
pig  iron  which  is  poured  into  it  from  a  side- tipping  ladle,  as 
shown  in  fig.  35.  The  alarm  is  sounded  and  the  air-blast  is 
turned  on.  The  vessel  is  rotated  until  in  a  nearly  upright 
position  and  the  blowing  is  continued  until  the  flame  drops  and 


90  IRON  AND   STEEL  MANUFACTURE. 

for  a  further  period,  the  length  of  which  is  decided  by  the 
"  blower  "  who  is  in  charge.  There  is  therefore  in  the  basic 
Bessemer  process  the  period  of  the  blow — till  the  flame 
"drops" — and  a  further  period  called  the  " after-blow."  It 
is  during  the  after-blow  that  nearly  all  the  phosphorus  is  eliminated, 
and  the  length  of  that  period  is  a  matter  for  cool  judgment. 

When  the  blower  thinks  the  after-blow  has  continued  long 
enough  he  has  the  vessel  turned  down  arid  the  blast  stopped. 
As  soon  as  the  "metal"  and  the  slag  have  separated  from 
each  other — and  as  they  are  both  very  fluid  and  the  difference 


Fig.  35. — Charging  Lime  into  a  Bessemer  Converter. 

in  density  is  great,  separation  is  soon  effected — a  sample  is 
withdrawn  by  means  of  a  long-handled  ladle  and  the  "  metal " 
sample  is  poured  into  an  open  mould  where  it  quickly 
solidifies.  The  sample  is  flattened  under  a  steam  hammer, 
water-cooled,  and  broken  across.  The  blower  examines  the 
fracture  and  judges  by  the  size  of  the  crystals  on  the  fractured 
parts  whether  or  not  the  process  of  dephosphorisation<-  has 
proceeded  far  enough.  If  not,  he  signals  for  the  continuance 
of  the  blow.  Another  sample  is  taken  and  similarly  tested. 
If.  in  the  judgment  of  the  blower,  this  is  still  unsatisfactory 


THE    BASIC    BESSEMER    PROCESS. 


91 


the  blowing  is  resumed — perhaps  for  some  seconds.  When 
he  concludes  that  the  metal  is  right  (due  allowance  being 
made  for  the  slight  rephosphorising  which  occurs  on  the 
addition  of  ferro-manganese  or  spiegel-eisen)  some  of  the  slag 
may  be  run  off.  The  necessary  amount  of  ferro-manganese 
or  spiegel-eisen  is  then  charged,  and,  when  it  has  had  time  to 
mix  well  with  the  metal,  the  steel  is  poured  into  the  hot, 
mounted  ladle  and  duly  teemed  into  the  moulds  which  have 
been  carefully  set  in  the  casting  pit.  The  treatment  of  steel 
ingots  is  dealt  with  in  Chapter  xiii. 

Additions  of  lime,  of  scrap,  or  of  iron  oxide  may  be  made 
at  a  certain  stage  or  stages  of  the  blow. 

The  Chemical  Changes  which  occur  during  the  basic  Bes- 
semer blow  may  be  gathered  from  the  following  table : — 


Com  position  of 

Constituents. 

Chemical 
Symbols. 

Pig  Iron 
Charged. 

Metal  at 
End  of 
Blow. 

Metal  at 
End  of 
After-blow 

Finished 
Steel. 

Graphitic  carbon, 
Combined  carbon, 

c 
c 

0-82 
2-83 

0-05 

Trace. 

6:14* 

Silicon, 

Si 

0-63 

0-03 

0-005 

001 

Phosphorus, 

P 

2-75 

2-38 

0-04 

0-04 

Sulphur,     . 

s 

0-07 

0-07 

0-05 

0-05 

Manganese, 

Mn 

1-75 

0-13 

o-io 

0-45 

Iron,  . 

Fe 

A 

A 

A 

A 

100-00 

100-00 

100-00 

100-00 

Chemical  Considerations. — The  elements  which  are  required 
to  be  removed  from  the  pig  iron  are  oxidised  by  the  oxygen 
of  the  air  which  is  forced  in  such  large  volume  through  the 
pig  iron  in  the  converter.  Silicon  and  carbon  are  vigorously 
attacked,  manganese  is  freely  acted  on,  and  when  these  are 
nearly  all  removed  iron  begins  to  be  burned,  and,  lastly,  the 
phosphorus  is  oxidised.  Where  abundance  of  hot  lime  is 
present  a  steady  diminution  of  the  amount  of  sulphur  in  the 

*  The  percentage  of  carbon  is  varied  according  to  requirements. 
A  By  difference. 


92  IRON   AND   STEEL    MANUFACTURE. 

metal  takes  place.  Prolonging  the  blow,  which  is  not  gener- 
ally advisable,  may  lead  to  a  further  diminution  of  sulphur. 
If  the  pig  iron  charged  contained  much  sulphur,  part  of  it 
may  be  easily  "  gasified  "  or  volatilised  and  carried  off"  in  the 
escaping  gases.  Hot  blows  tend  to  lead  to  sulphur  elimina- 
tion. Where  only  a  moderate  amount  of  sulphur  is  present 
it  appears  that  that  which  is  removed  during  the  after-blow 
all  goes  into  the  slag.  In  one  British  Bessemer  work  about 
33  per  cent,  of  sulphur  is  regularly  eliminated  during  blowing. 

The  Chemical  Reactions  may  be  indicated  by  the  following 
equations  :  — 

Si          +  02  Si02 

Silicon      and      oxygen      yield      silica, 

which  combines  with  bases  in  the  slag. 

Carbon  is   oxidise4,  forming  carbon  monoxide   (CO)   and 
carbon  dioxide  (C02),  thus  — 

2C          +          02  =  2CO 

Carbon      and      oxygen      yield      carbon  monoxide. 

C  +  02  =  C02 

Carbon      and      oxygen      yield        carbon  dioxide. 

These  oxides  being  gaseous  escape  by  the  open  mouth  of  the 
converter. 

S  +  02  S02 

Sulphur      and      oxygen      yield      sulphur  dioxide. 

The  sulphur  dioxide  escapes  with  the  other  gases. 

Sulphur  trioxide  (S03)  may  be  formed  by  the  action  of 
ferric  oxide—  - 

9Fe203        +  S  6Fe3O4         +  S03 


The  sulphur  trioxide  combines  with  lime  in  the  slag. 

S03  +        CaO         =  CaS04 

Sulphur  trioxide      and      lime      form      calcic  sulphate. 


THE    BASIC    BESSEMER    PROCESS.  93 

Manganese  is  oxidised,  and  the  resulting  oxide  goes  into 
the  slag : — 

Mn  +            0            =                    MnO 

Manganese,  and      oxygen      yield      manganous  oxide. 

Two  oxides  of  iron  are  formed,  and  they  constitute  part  of 
the  slag : — 

2Fe         +  O2  2FeO 

Iron      and      oxygen      yield     ferrous  oxide. 

4Fe         +  302  2Fe203 

Iron      and      oxygen      yield       ferric  oxide. 

Phosphorus  when  oxidised  forms  phosphoric  acid  (more 
correctly  named  phosphoric  anhydride) : — 

4P  +          502  2P206 

Phosphorus      and      oxygen      yield      phosphoric  acid. 

The  phosphoric  compound  unites  with  lime  to  form  tetra- 
calcic  phosphate : — 

P206  +       4CaO       =  4CaO.PflO5 

Phosphoric  acid      and      lime     form     tetra-calcic  phosphate. 

Tetra-calcic  phosphate  was  discovered  simultaneously  by 
Hilgenstock  in  Germany,  and  Stead  &  Bidsdale  in  England. 
So  far  it  has  not  been  found  in  nature. 

The  acids  in  the  basic  slag  are  silica  (Si02)  and  phosphoric 
anhydride  (P206).  The  bases  present  are  lime  (CaO), 
magnesia  (MgO),  manganous  oxide  (MnO),  and  ferrous 
oxide  (FeO).  To  carry  on  the  process  a  decided  excess 
of  base  must  be  present  in  the  converter. 

At  the  end  of  the  after-blow  the  "  metal "  is  in  a  highly 
oxidised  state,  and  the  addition  of  suitable  material  containing 
manganese  and  carbon  is  necessary.  The  finishing  material 
is  added  as  in  the  acid  Bessemer  process,  and  the  reactions — 
detailed  on  pp.  78,  79,  and  80 — and  effects  are  similar. 

Recarbnrising. — There  is  danger  of  reduction  of  some 
phosphorus  from  the  slag  during  recarburising.  To  lessen 
this  risk  the  slag  is  freely  poured  off  before  "  finishing."  As 


94 


IRON    AND    STEEL    MANUFACTURE. 


the  bath  of  metal  is  highly  oxidised  it  is  not  unusual  to  add 
grey  hematite  pig  iron  (which  is  rich  in  carbon  and  silicon) 
before  adding  ferro-manganese  or  spiegel-eisen. 

In  the  basic  Bessemer,  as  in  other  modern  steel-making 
processes,  ferro-manganese  is  used  for  mild  steels,  while 
spiegel-eisen  is  employed  when  higher  carbon  steels  are  being 
made.  Carbon  is  added  directly  in  some  instances.  The 
carbon,  or  molten  spiegel-eisen,  is  added  to  the  metal  which 
had  been  poured  into  the  ladle  with  the  smallest  workable 
quantity  of  slag. 

Comparison  of  the  composition  of  the  pig  iron  used  for  the 
respective  processes  : — 


Constituents. 

Chemical 
Symbols. 

Acid 
Bessemer. 

Basic 
Bessemer. 

Per  cent. 

Per  cent. 

Graphitic  carbon, 

c 

3-42 

0-82 

Combined  carbon, 

c 

0-46 

2-83 

Silicon, 

Si 

2-20 

0-63 

Phosphorus, 
Sulphur, 

P 

s 

0-045 
0-045 

2-75 
0-07 

Manganese, 

Mn 

0-47 

1-75 

Iron,   . 

Fe 

A 

A 

100-00 

100-00 

. 

It  may  be  noticed  at  a  glance  that  the  basic  pig  iron  is  high 
in  combined  carbon,  in  phosphorus,  and  in  manganese.  The 
silicon  in  it  is  low,  and  for  a  good  reason,  namely — the  result 
of  oxidising  silicon  is  the  production  of  silica,  which,  being 
acid,  is  undesirable  in  large  amount  in  the  slag.  The  maker 
of  basic  pig  iron,  therefore,  keeps  the  silicon  in  the  pig  iron  as 
low  as  he  can.  In  pig  irons  which  do  not  contain  much 
silicon,  most  of  the  carbon,  as  a  rule,  exists  in  the  combined 
state. 

There  is  considerable  amount  of  manganese  in  good  basic 
pig  iron,  because 

(a)  Presence  of  much  manganese  tends  to  keep  the  per- 
centage of  sulphur  low. 


THE    BASIC    BESSEMER    PROCESS. 


(b)  Because  the  manganese,  while  undergoing  oxidation  in 
the  converter,  makes  good,  as  far  as  possible,  the  heat 
which  would  have  been  derived  from  the  presence  of 
silicon.  Manganese  oxide  (MnO)  being  basic,  is  not 
so  objectionable  in  the  slag. 

But  the  chief  feature  in  the  comparison  is  the  large  amount 
of  phosphorus  in  the  basic  pig  iron.  The  percentage  of  phos- 
phorus is  high,  because 

(a)  Puddlers  tap    (tap    cinder),  from  which  it  is  largely 

made,  is  comparatively  cheap,  and  contains  much 
phosphorus  as  well  as  iron. 

(b)  A  large  amount  of  phosphorus  is  necessary  to  maintain 

the  needed  high  temperature  in  the  converter  during 
the  continuance  of  the  after-blow,  and  the  heat  can  be 
had  by  the  oxidation,  or  burning,  of  a  comparatively 
large  quantity  of  phosphorus. 

.  (c)  The  higher  the  percentage  of  phosphorus  in  the  pig  iron 
the  richer,  under  ordinary  conditions,  will  the  slag  be 
in  phosphoric  acid,  and  the  higher  will  be  the  price 
obtainable  for  the  slag.  With  each  increase  in  per- 
centage of  phosphoric  acid  there  is  a  very  considerable 
increase  in  market  value.  The  basic  pig  iron  is 
purposely  enriched  in  phosphorus  by  using  mineral 
phosphate  in  its  production.  Under  certain  circum- 
stances, such  as  a  very  hot  blow,  a  little  of  the 
phosphorus  may  escape  in  the  outgoing  gases. 

APPROXIMATE  COMPOSITION  OF  GOOD  QUALITY  BASIC  BESSEMER  SLAG. 


Constituents. 

Chemical  Formulae. 

Percentage. 

Phosphoric  acid, 

P20e 

20 

Silica,      . 

SiO2 
CaO 

6 
46 

Magnesia, 
Ferrous  oxide, 

MgO 
FeO 

6 
13 

Ferric  oxide,  . 

Fe203 

2 

Manganous  oxide, 
,     Alumina,  &c., 

MnO 
A1A,  Ac. 

5 
2 

100 

96  IRON   AND   STEEL   MANUFACTURE. 

When  the  slag  has  cooled  down  it  is  broken  up,  ground  to 
a  very  fine  powder,  placed  in  bags,  and  sold  as  a  fertiliser. 
Eeduction  to  powder  may  be  effected  by  grinding,  or  by  the 
action  of  superheated  steam.  The  lime,  and  especially  the 
phosphoric  acid,  in  the  slag,  make  it  highly  valuable  for 
certain  soils  and  crops. 

The  greater  the  percentage  of  easily  soluble  phosphoric  acid 
in  the  slag  the  higher  is  the  price  it  will  fetch.  And  justly 
so,  because  such  soluble  slags  will  yield  a  quicker  and  a  greater 
return  to  the  farmer :  a  quicker  return,  because  the  plants 
grown  in  the  field  which  is  enriched  with  this  fertiliser  will 
more  easily  assimilate  it,  and  be  thereby  helped  in  healthy 
growth ;  and  a  greater  return,  because  there  will  be  less  of  the 
precious  phosphoric  acid  left  in  the  ground,  with  the  possibility 
of  much  of  it  being  washed  by  the  winter's  rain  so  deeply  into 
the  soil  as  to  get  beyond  the  reach  of  the  roots  of  the  next 
year's  crop. 


97 


CHAPTER     X. 

PLANT   AND    APPLIANCES   FOR   THE    SIEMENS- 
MARTIN    OR   OPEN-HEARTH   PROCESS. 

MILD  or  medium  steels  are  regularly  made  in  charges  of 
5  tons  and  upwards.  The  smaller  furnaces  are  for  making 
steel  castings.  30-,  40-,  and  50-ton  charges  are  now  common, 
and  furnaces  for  160  tons,  and  even  for  200  tons,  are  built 
and  at  work. 

The  fuel  used  in  this  process  is  either  producer  gas. 
which  is  specially  made  in  gas  producers,  or  natural  gas  as 
found  in  certain  territories  in  the  United  States.  The  regen- 
erative system — a  system  suggested  and  practically  applied 
to  an  engine  by  the  Eev.  Dr.  STIRLING — is  adopted,  so  as 
to  utilise  in  the  furnace  as  much  as  possible  of  the  heat 
generated. 

Gas  Producers. — A  gas  producer  is  designed  to  burn  solid 
fuel  in  such  a  manner  as  to  convert  as  much  as  practicable 
of  it  into  combustible  gases,*  which  can  be  collected,  conveyed, 
and  used  where  required. 

When  coal  slack  or  other  suitable  fuel  is  charged  into  a 
producer  which  has  been  made  hot  and  is  in  working  order, 
the  fixed  carbon  (C)  which  it  contains  is  converted  into  carbon 
dioxide  (C02),  and  the  dioxide  is  reduced  to  carbon  monoxide 
(CO)  if  a  moderate  supply  of  air  has  access  to  plenty  of  glowing 
fuel.  Hydrocarbons,  such  as  methane  or  marsh  gas  (CH4)r 
are  liberated  from  the  solid  fuel,  and  hydrogen  (mostly 
from  the  decomposition  in  the  producer  of  the  steam  which 
is  used  to  impel  the  air  blast)  is  also  found  in  the  pro- 
ducer gas  (see  analysis  on  p.  246). 

These  three  components  (carbon  monoxide,  methane,  and 
hydrogen)  are  all  combustible,  and  the  value  of  the  producer 
gas  will  depend  on  the  quantity  of  these  in  its  composition. 

*  Gases  which  can  be  burned. 

7 


98 


IRON    AND    STEEL   MANUFACTURE. 


The  Siemens  G-as  Producer  consists  of  a  rectangular  com- 
partment built  of  brick  walls,  with  fire-bars.  Four  compart- 
ments make  up  a  block  and  several  blocks  may  be  built 
together.  Over  each  compartment  is  a  hopper  by  which 
the  coal  slack,  or  other  fuel  which  is  to  be  gasified,  is 
charged  into  the  producer.  Air  may  be  admitted  between 
the  fire-bars,  but  the  general  practice  is  to  close  the  opening 
in  front  of  the  ashpit  and  inject  air  by  the  force  of  one 


Fig.  36.— Wilson  ,Gas  Producer— Section. 

or  two  steam  jets.  A  water  trough  is  provided  for  the 
ashes.  The  gas  which  is  produced  is  collected  and  conveyed 
by  an  overhead  main  pipe  or  by  culverts  (underground 
passages)  to  the  furnaces. 

The  Wilson  Gas  Producer  is  an  upright  cylindrical  structure 
of  mild  steel  plates  lined  with  fireclay  bricks  or  blocks.     It 


OPEN-HEARTH    PLANT. 


is  shown  in  section  in  fig.  36.  The  solid  fuel,  from  which 
the  gas  is  to  be  made,  is  charged  in  by  a  hopper — a  hollow 
tapered  iron  casting  which  is  bolted  to  the  top  of  the 
producer.  A  cone  closes  the  passage  from  the  hopper  to 


Fig.  37.— Wilson  Gas  Producer  with  Water  Bottom. 


100  IRON"    AND    STEKL    MANUFACTURE. 

the  producer,  and  a  lid  covers  the  hopper.  The  hopper  is 
filled  with  fuel,  and,  when  it  is  intended  to  discharge  it,  the 
lid  is  shut  down  and  the  cone  is  allowed  to  descend.  The 
fuel  is  thus  admitted  to  the  producer,  the  cone  causing  an 
equal  distribution  of  the  slack  or  other  fuel  used.  As  the 
fuel  burns*  the  charge  is  in  due  course  decomposed,  and 
every  part  of  it  except  the  ash  is  converted  into  gas.  The 
gas  is  drawn  off  by  suitable  ports  or  openings  to  the  downtake, 
from  whence  it  is  conveyed  by  culverts  or  pipes.  Air  is  forced 
in  by  means  of  an  injector  consisting  of  a  steam  jet  and 
a  pipe  with  an  enlarged  entrance.  The  amount  of  air  and 
steam  can  easily  be  regulated.  They  are  forced  through 
the  pipe  into  a  horizontal  brick  passage — the  distributor — 
above  the  flooring  of  the  producer  and  distributed  through 
openings  for  that  purpose  in  the  brick  passage. 

The  producer  has  a  solid  bottom,  and,  when  it  is  necessary 
to  clear  out  ashes,  iron  bars  are  inserted  at  a  certain  height 
so  as  to  keep  the  unconsumed  fuel  up  while  the  ashes  are 
withdrawn  through  the  cleaning  door. 

"  Solid  bottom  producers  are  cleaned  out  at  intervals  varying 
from  12  to  48  hours  apart,  according  to  the  quality  of  the 
coal  and  the  amount  of  work  they  are  doing.  This  does  not 
by  any  means  involve  emptying  the  producer  of  fuel.  The 
bottom  doors  are  opened  after  stopping  the  blast,  &c.,  and  the 
ash  and  refuse  at  the  bottom  are  raked  out.  The  doors  are 
then  closed  and  gas-making  resumed ."f 

In  a  later  design  the  producer  is  set  on  a  long  water  trough,, 
as  shown  in  fig.  37.  Near  the  bottom  of  the  producer  the 
inner  space  is  contracted  so  that  the  unconsumed  fuel  is  held 
up,  but  as  it  burns  away  the  ash  drops  into  the  water  in  the 
trough  below.  A  plate  suited  to  the  curvature  dips  from  the 
contracted  part  into  the  water  lute  and  prevents  the  escape 
of  gas.  Water-bottom  producers  are  worked  continuously, 
the  clinker  and  ashes  being  withdrawn  from  the  trough  from 
time  to  time.  To  make  sure  that  sufficient  is  being  with- 
drawn to  keep  the  producer  clean  and  in  the  best  working 
order,  it  is  necessary  in  this  arrangement  to  go  on  shovelling 
ash  out  until  more  or  less  unburnt  fuel  comes  down. 

*  A  fire  must  be  kindled  in  the  producer  on  starting  it  to  work, 
t  Power  Gas  Plant,  by  Alfred  Wilson,  p.  25. 


OPEN-HEARTH    PLANT.  101 

The  Wilson  water-bottom  producer  with  constant '  a\sh- 
removing  gear  is  shown  in  section  in  fig.  38.  As  in  the 
solid-hearth  producer,  there  are  no  fire-bars.  The  solid 
matter  sinks  down  through  water  inside  the  lower  part  of 
the  producer  and  is  forced  out  by  an  Archimedian  screw 
arrangement  and  up  an  inclined  plane  to  the  outside,  no  gas 


Fig.  38. — Wilson  Gas  Producer  with  Archimedian  Screw  for 
removing  ashes. 

being  able  to  escape.  The  screw  is  caused  to  constantly 
revolve  very  slowly,  being  driven  by  suitable  gearing  from  a 
shaft. 

The    screws    or    worms    are    made    tapering,    the    largest 
diameter  being   at   the  outlet  end;    their  blades  are  also  of 


102  IftCN    AND    STEEL    MANUFACTURE. 

increasing  pitch  -towards  the  same  end,  and  by  this  arrange- 
ment nothing  can  stick  in  the  screw.  There  is  a  considerable 
evaporation  from  the  water  at  the  bottom  as  the  hot  ashes 
gradually  descend  into  it.  The  steam  is,  however,  decomposed 
higher  up,  and  serves  to  increase  the  percentage  of  hydrogen 


Fig.  39.— A.  B.  Duff  Gas  Producer. 

in  the  resulting  gas.  Owing  to  the  constant  agitation  of  the 
fuel  by  the  revolving  worm  the  production  of  gas  is  uniform, 
and  good  working  is  secured. 

The  A.  B.  Duff  Producer,  which  is  so  much  in  favour  at 
home,  on  the  Continent,  and  in  America,  has  a  thick  lining 


OPEN-HEARTH    PLANT.  103 

»f  fireclay  blocks  encased  in  a  sheathing  of  malleable  plates. 
It  is  of  the  upright  cylinder  type,  and  is  surmounted  by 
a  hopper  through  which  the  fuel  is  fed  in  to  work  its 
way  steadily  downwards.  The  whole  structure  is  set  on 
a  water  bottom.  A  sketch,  partly  in  section,  is  shown  in 
fig.  39. 

The  necessary  air,  which  is  often  preheated,  is  injected  by 
steam,  and  enters  the  producer  by  a  circular  central  tower 
having  slotted  cast-iron  plates  for  its  sides  and  a  roof 
arranged  to  permit  the  passage  of  air  between  its  upper  and 
lower  parts.  An  efficient  distribution  of  air  is  thus  ensured. 
The  central  tower  contracts  the  space  and  thus  causes  the 
fuel  (already  somewhat  swollen  and  caked  together  by  heat) 
to  be  held  up  until  the  combustible  components  are  converted 
into  gases  by  the  action  of  the  injected  air.  The  gases 
thereby  produced  ascend  and  are  conveyed  by  the  downtake 
to  a  culvert.  The  ash  drops  into  the  water  bottom,  from 
whence  it  is  raked  out  without  deranging  or  stopping  the 
gas-making. 

The  Gas  Valves  are  of  two  kinds:  mushroom  valves  for 
regulating  the  amount  of  gas,  and  butterfly  valves  for 
determining  the  direction  of  the  air  and  the  gas.  Many 
patent  gas  valves  are  in  use. 

Open-hearth  furnaces  are  either  stationary  or  movable,  the 
latter  being  known  as  rolling  or  tilting  furnaces  (see  p.  255). 

The  Stationary  Open-hearth  Furnace  is  a  huge  oblong 
structure  built  of  silica  bricks  cemented  with  suitable  mortar 
arid  braced  with  buckstaves  and  tie-rods  and  set  over  five 
arches.  Of  these  arches  the  central  one  is  left  blank,  the 
two  arches  next  to  the  central  one  are  for  air  regenerators, 
and  the  outer  two  are  for  gas  regenerators.  But  the 
inner  ones  may  be  arranged  for  gas  and  the  outer  ones 
for  air.  These  regenerative  chambers  contain  firebricks, 
which  are  packed  checkerwise  in  such  a  manner  as  to 
expose  as  much  surface  of  brick  as  possible  while  allowing 
free  passage  for  gas  or  for  air.  The  bricks  absorb  heat 


_. 


OPEN-HEARTH    PLANT.  105 

from  the  outgoing  (hot)  gases  and  impart  heat  to  the  ingoing 
(cold)  air  and  gas. 

Fig.  40  shows  the  front  view  of  furnaces  at  the  Norfolk 
Works  of  Messrs.  Thomas  Firth  &  Son,  Sheffield. 

The  chambers  communicate  with  passages  both  at  top  and 
bottom;  the  top  passage  of  each  ascending  from  its  re- 
generator to  port,  or  ports,  at  its  own  end  of  the  furnace. 
Each  end  of  the  furnace  includes  an  outer  and  an  inner  wall. 
The  latter  may  be  straight  across  or  be  built  with  a  slight 
curvature.  The  upright  passages  leading  from  the  re- 
generators are  built  between  the  two  end  walls,  like  an 
ordinary  domestic  chimney,  but  in  this  case  terminating  at 
the  top  of  the  ports.  The  ports  are  openings  (constructed 
with  a  slight  slant)  in  the  inner  wall;  they  lead  from  the 
upward  passages  to  the  inside  of  the  furnace.  There  may  be 
one  gas  and  one  (larger)  air  port  at  each  end.  or  there  may  be 
three  air  ports  and  two  gas  ports,  or  two  gas  ports  and  one 
wide  air  port.  The  air  ports  are  at  a  higher  level  than  the 
gas  ports.  At  each  end  of  the  furnace  the  ports  and  passages 
correspond  in  arrangement,  number,  and  size  with  those  at  the 
other  end. 

When  the  furnace  is  at  work,  producer  gas  is  conveyed 
through  one  of  the  gas  regenerators  *  to  its  port  or  ports, 
and  air  is  conveyed  through  the  neighbouring  air  regenerator 
to  its  port  or  ports.  Where  the  gas  and  air  meet  in  the  hot 
furnace,  ignition  immediately  takes  place — just  as  when  gas  is 
lit  at  an  ordinary  gas  burner — and  a  long  sheet  of  flame 
sweeps  along  and  heats  the  furnace,  much  heat  being,  in  time, 
deflected  from  the  roof.  The  hot,  spent  gases  (the  products 
of  combustion)  pass  out  at  the  opposite  ports,  and,  proceeding 
by  proper  channels  to  the  top  of  the  regenerators  at  what  is 
then  the  outgoing  end,  impart  much  heat  to  the  checkered 
packing  of  bricks  in  the  regenerators,  and  are  drawn  off  by 
passages  left  under  the  checker  work  of  the  regenerators,  and 
under  the  valve  pit,  to  the  chimney.  The  chimney  is  usually 
a  cylindrical  brick  structure,  about  50  feet  or  so  in  height, 
encased  in  ri vetted  plates.  It  is  set  on  a  firm  base  and  is 
stayed  by  stout  wire  cables.  In  the  base,  arrangements  are 

*  Natural  gas,  being  rich  in  combustible  component?,  does  not  require 
to  be  passed  through  a  regenerative  chamber. 


106 


IRON   AND    STBEL    MANUFACTURE. 


OPEN-HEARTH    PLANT.  107 

made  for  kindling  a  fire  to  create  a  "draught"  sufficient  to 
"  pull "  the  products  of  combustion  through  the  furnace  and 
regenerators  when  lighting,  drying,  and  starting  the  furnace 
when  new  or  after  repairs.  The  "draught"  is  moderated, 
when  required,  by  the  use  of  a  damper. 

Beside  each  of  the  four  checkered  chambers  is  a  receptacle 
known  as  a  slag  pocket  or  dust  catcher.  The  slag  pocket 
is  intended  to  retain  fine  particles  of  dust — iron  ore  dust, 
lime  dust,  &c. — and  an  occasional  overflow  of  slag.  The  dust 
is  liable  to  be  carried  over  in  the  current  from  the  furnace 
and  would  flux  and  clog  the  "  checkers  "  and  interfere  with 
the  storing  up  of  heat,  causing  thereby  inconvenience  and 
expense. 

To  return  to  the  consideration  of  the  regenerative  system : 
When  the  flame  has  continued  to  travel  in  one  direction  for 
about  20  or  30  minutes,  the  valves  are  reversed  and  the  gas 
and  air  are  caused  to  pass  upwards  through  the  regenerators 
which  have  been  heated  by  the  outgoing  gases. 

The  ingoing  gas  and  air  are  thus  preheated  and  yield 
a  hotter  flame.  The  outgoing  spent  gases  pass  out  at  the 
ports  which  were  formerly  inlet  ports  and  descend  between 
the  checkered  brickwork  in  the  corresponding  regenerators 
which  are  thus  heated  highly.  Again,  in  due  course,  the 
valves  are  reversed,  and  with  each  reversal  the  furnace 
becomes  more  highly  heated,  until  a  temperature  which  can 
melt  steel  is  attained.  Such,  in  brief  outline,  is  the  regenera- 
tive system. 

The  sides  of  the  furnace  are  strengthened  by  iron  plates 
and  castings.  Buckstaves — which  are  often  made  of  old 
rails — are  set  upright  at  intervals  and  "tied"  by  tie-rods, 
which  are  screwed  at  the  ends  to  suit  large  nuts,  to  the 
buckstaves  opposite.  These  tie-rods  extend,  above  the  roof, 
from  end  to  end  and  from  side  to  side.  Two  tie-rods  also 
reach,  in  diagonal  directions,  from  strong  supports  at  the 
corners,  thus  adding  strength  to  the  structure. 

As  the  roof  of  the  furnace  is  built  of  bricks  it  would  be 
impossible  in  practice  to  keep  it  from  falling  in  if  it  were 


108 


IRON    AND    STEEL    MANUFACTURE. 


A, 
B, 

C, 

D, 

K, 

F, 

O, 

H, 

I, 

J, 

K, 

L, 


built  flat.  It  is,  therefore,  arched  across.  And  as  the  bricks 
expand  very  much  on  being  heated,  and  contract  considerably 
on  cooling,  the  nuts  at  the  ends  of  the  tie-rods  are  gradually 
loosened  when  the  furnace  is  being  heated  up  for  a  campaign 
and  tightened  as  the  furnace  cools  down  at  the  close.  The 
general  rise  and  fall  of  temperature  during  ordinary  working 


J     K 


K      J 


Fig.  42. — Siemens  Furnace — Cross  Section. 


Wheel  for  rotating  casting  ladle. 

Ladle. 

Ingot  mould. 

Casting  pit. 

Slag  ladle. 

Launder. 

Tapping  spout. 

Taphole. 

Wall. 

Air  port. 

Gas  port. 

Buckstave. 


M,  Charging  door. 

N,  Foreplate  or  sill. 

O,    Working  lining. 

P,    Firebricks. 

Q,    Charging  platform  of  iron  plates. 

R,   Butterfly  valve  for  air. 

S,    Flap  for   regulating  amount   of 

air. 

T,   Butterfly  valve  for  gas. 
U,  Valve  for  regulating  amount  of 

gas. 
V,  Culvert  for  gas  from  producers. 


causes  expansion  and  contraction,  and  the  arching  of  the  roof 
allows  a  slight  but  sufficient  rising  or  depressing  along  the 
centre  and  at  other  parts  of  the  roof  as  required. 

The  bottom  of  the  furnace  consists  of  iron  plates  or  castings 
which  are  carried  on  strong  steel  girders  supported  on  brick- 


110  IRON   AND   STEEL   MANUFACTURE. 

work,  or,  better  still,  on  columns.  Cast-iron  plates  make  up 
a  long  deep  tray  with  sloping  sides.  On  the  tray  good  bricks 
are  set  so  as  to  form  an  outline  somewhat  resembling  an  oval 
basin.  Over  the  bricks  the  working  lining  of  sand  coated 
with  slag  is  laid  in  the  manner  described  on  p.  11 4. 

On  the  front  or  charging  side  there  are  generally  three 
openings,  and  on  the  tapping  side  two  openings.  These  can  be 
closed  by  doors,  which  consist  of  silica  bricks  set  in  strong  iron 
frames.  The  iron  frames  are  made  larger  than  the  openings  so 
that  they  are  not  directly  exposed  to  the  high  temperature  of 
the  furnace.  The  doors  may  be  raised  or  lowered  mechanically 
or  by  hand.  If  by  the  latter  they  are  suspended  from  the 
shorter  portion  of  a  lever,  on  the  longer  portion  of  which  is  a 
counterpoise  which  nearly  balances  the  weight  of  the  door. 
In  the  centre  of  some  doors  there  is  a  peep-hole  through 
which  the  progress  of  the  process  can  be  observed.  A  disc 
or  plate  covers  the  peep-hole  between  observations.  Through 
the  three  doors  on  the  front  side  the  solid  materials  are 
usually  charged,  and  the  charge  is  rabbled  when  required. 
Samples  are  withdrawn  through  the  central  front  door.  All 
doors  admit  repairing-material  and  tools.  At  the  bottom  of 
each  door  is  a  thick  projecting  sill  or  foreplate  of  cast  iron. 

The  Shoot  or  Launder,  along  which  the  steel  arid  slag  are 
conveyed  from  the  taphole  to  the  ladle,  is  a  half-round  gutter 
made  of  steel  plates.  It  is  often  in  two  parts — a  short  one 
which  slopes  sharply,  and  a  longer  one  which  is  set  with  a 
slope  which  is  not  so  steep.  The  short  one  is  fixed  to  the 
furnace,  the  long  one  rests  on  trunnions.  They  are  well  lined 
with  a  thick  coating  of  ganister;  the  joining  of  the  two  is 
carefully  made,  and  the  whole  is  thoroughly  dried  and  warm 
when  the  furnace  is  tapped.  Fig.  43  shows  a  view  of  the 
back  or  "  tapping  side  "  of  one  of  the  Siemens  furnaces  at  the 
Rutland  Works  of  Messrs.  Samuel  Osborn  &  Son,  Sheffield. 

Movable  (rolling  or  tilting}  furnaces  are  described  in  the 
appendix. — See  page  255. 

The  Casting  Pit  for  the  Siemens-Martin  process  is  generally 
in  a  straight  line  behind  the  row  of  open-hearth  furnaces. 
Rails  are  laid  on  the  tops  of  the  two  long  walls  of  the  casting 
pit  (fig.  44),  and  on  these  rails  a  four-wheeled  bogey,  carry- 
ing the  casting  ladle,  travels  when  pushed  or  pulled  by  a 


I 

I 


OPEN-HEARTH    PLANT.  Ill 

travelling  engine  running  on  rails  which  are  parallel  to  the 
pit.  The  Travelling  Engine  or  Crane  Locomotive  oi  the  kind 
made  by  Messrs.  Andrew  Barclay,  Sons  &  Co.,  Kilmarnock, 
and  illustrated  on  opposite  page,  is  employed  for  setting  the 
ingot  moulds,  stripping  and  removing  the  ingots,  &c. 

The  Ladle  is  of  the  Bessemer  type,  is  brick-lined,  and  has 
rod,  stopper,  and  nozzle.*  It  is  mounted  on  a  four-wheel 
bogey,  which  can  be  caused  to  travel  on  the  rails  at  the  casting 
pit.  The  large  ladle,  as  made  by  the  Lilleshall  Company, 


Fig.  44. — Siemens  Casting  Pit,  with  Ladle  in  the  distance. 

shown  in  fig.  45,  has  double  stopper  arrangements,  so  that, 
when  teeming,  two  ingots  may  be  run  at  the  same  time. 

Preparing  the  Furnace. — When  a  furnace  has  been  built  or 
repaired,  a  lining  of  firebricks  is  placed  on  the  bottom  plates, 
and  additional  bricks  are  laid  so  as  to  form  an  oval  hollow. 
The  furnace  is  then  carefully  dried,  the  gas  introduced  with 
caution,  the  working  lining  patiently  put  in,  and  the  taphole 
made  up. 

*  See  description  of  Bessemer  ladle  on  p.  68. 


OPEN-HEARTH    PLANT.  113 

To  dry  the  furnace,  a  fire  is  kindled  in  the  temporary  fireplace 
in  the  chimney,  and  fires  are  also  kindled  in  the  regenerative 
chambers.  In  about  two  days  the  chimney  and  chambers  may 
be  partially  dried;  the  fires  are  then  withdrawn  from  the  cham- 
bers. Long  fireclay  bricks  are  then  built  (without  mortar  or 
other  setting)  to  form  supports  on  which  bricks  are  piled  in 
open  order  to  make  up  the  checker  work  in  the  regenerators. 
A  fire  is  then  kindled  in  the  furnace,  air  being  admitted 
through  the  doors,  and  the  hot  products  of  combustion  drawn 
downwards  through  the  four  air  and  gas  regenerators  to  the 
passages  leading  to  the  chimney.  When  the  furnace  is  ready, 
gas  from  the  producers  is  allowed  to  blow  through  the  culvert 
as  far  as  the  outlet  nearest  to  the  furnace,  in  order  to  clear 
the  air  out  of  the  culvert.  Quick-burning  materials,  such  as 
shavings,  splinters  of  dry  wood,  &c.,  are  heaped  in  the  furnace 
so  as  to  fill  it  with  flame  and  pass  much  carbon  dioxide  into 
the  regenerators  at  the  outgoing  end.  The  doors  are  all 
closed,  and  gas  from  the  producers  is  cautiously  admitted; 
and,  under  these  conditions,  it  should  ignite  gently.  Careless- 
ness or  laziness  in  preparing  to  admit  gas  is  unpardonable. 
For  want  of  ordinary  prudence  the  furnace  and  checker  work 
may  be  shaken,  and  the  whole  campaign  carried  on  under  ad- 
verse conditions  on  account  of  an  easily-preventable  explosion. 

When  the  gas  has  become  ignited,  more  air  is  admitted 
to  the  furnace  by  opening  the  doors  a  little,  and,  afterwards, 
a  regulated  quantity  is  supplied  through  the  air  regenerator. 
After  about  seven  hours  the  current  may  be  reversed,  the  gas 
being  followed  a  few  minutes  after  by  a  gentle  passage  of  air 
through  the  neighbouring  regenerator.  The  gas  and  air  valves 
are  subsequently  reversed  from  time  to  time  at  lessening 
intervals. 

As  the  temperature  of  the  furnace  rises  the  bricks  expand, 
and  the  nuts  at  the  end  of  the  tie-bolts  must  be  turned  so  as 
to  allow  the  buckstaves  to  give  way  a  little.  Otherwise  the 
roof  would  become  dangerously  distorted,  and  the  stability  of 
the  furnace  would  be  impaired. 

When  the  heat  in  the  furnace  is  sufficient  to  frit  *  sand,  the 
first  sprinkling  of  the  working  lining  is  put  in.  The  working 

*  Frit,  from  a  Latin  word  signifying  to  roast,  means  in  metallurgy  to 
soften  by  heat,  so  that  the  particles  stick  together. 

8 


114  IRON    AND   STEEL    MANUFACTURE. 

lining  consists  of  white  Belgian  sand  with  an  admixture  of 
less  pure  sand,  or  of  loam,  as  a  binding  material. 

To  make  up  the  required  thickness  of  sand  lining  a  thin 
layer  of  the  mixture  is  spread  over  the  bricks,  and,  when  the 
heat  of  the  furnace  has  caused  the  sand  particles  to  firmly 
stick  to  each  other,  another  sprinkling  of  sand  is  thrown  in 
which  "  frits  "  or  melts  just  enough  to  cause  the  sticking  of 
the  grains  to  each  other  and  to  the  layer  beneath.  In  that 
way,  by  "  shifts  "  working  day  and  night  for  about  a  week,  the 


Fig.  46. — Tapping  a  Siemens  Furnace. 

working  bottom  (bed  and  banks)  is  built  up  little  by  little. 
When  the  bricks  are  covered  with  a  thick  enough  lining — 
which  is  continued  until  it  rests  also  on  the  silica  bricks  of 
which  the  furnace  walls  are  composed — pieces  of  Siemens 
(acid)  slag  are  scattered  over  the  surface.  The  slag  melts 
and  sinks  a  little  into  the  sand  lining,  forming  a  glaze  over 
the  surface. 

The  working  lining  of  the  furnace  is  shaped  so  as  to  slope 
towards  the  taphole,  at  the  centre  of  the  tapping  side — that 
is,  the  side  at  which  the  metal  is  tapped,  or  discharged,  when 
ready.  Before  charging  the  furnace  the  taphole  is  well 
rammed  with  a  mixture  of  crushed  anthracite  and  sand,  firmly 
enough  to  prevent  a  breaking  out  of  the  melted  charge,  yet 


OPEN-HEARTH     PLANT.  115 

not  jammed  so  tightly  as  to  cause  a  "  hard  tap."  A  hard  tap 
occasions  undue  delay  when  the  metal  is  ready  for  the  ladle. 
When  required,  the  taphole  is  opened  by  means  of  a  pointed 
rod  and  a  sledge  hammer.  The  rod  is  driven  in  from  the 
outside,  a  ring  is  slipped  on,  and  a  wedge  inserted  between 
the  rod  and  the  ring  with  its  thin  end  towards  the  ladle.  Gn 
hammering  the  wedge  the  rod  is  forced  out,  and  the  opening 
made  is  widened  by  means  of  a  rod  worked  through  from  the 
charging  side  of  the  furnace. 

After  the  metal  and  slag  have  been  tapped  out,  the  sand 
bottom  is  repaired  by  fritting  sand  where  hollows  have  formed. 
All  slag  is  carefully  cleared  away  from  about  the  taphole. 

To  make  up  the  taphole  for  the  next  charge  an  iron  tool, 
consisting  of  a  long  rod  with  a  plate  or  an  enlargement  at 
one  end,  is  used.  The  larger  end  of  the  rod  is  pressed  against 
the  inner  end  of  the  taphole,  which  is  then  firmly  rammed 
with  the  usual  mixture  of  sand  and  crushed  anthracite. 

A  Siemens  furnace  is  not  usually  hurried  in  the  working  of 
its  earlier  charges :  it  generally  does  its  best  work  in  the 
second  week  of  its  campaign,  which,  as  a  rule,  lasts  about  ten 
weeks  before  the  furnace  requires  partial  repair. 

Parts  which  wear  away  quickly  are  patched  up  where  they 
can  be  got  at.  Should  a  part  of  the  roof  give  way,  a  "  crab  " 
—that  is,  a  flat  iron  clamp,  or  clamps,  embracing  a  number 
of  silica  bricks — is  placed  over  the  worn  part. 

For  charging  the  furnaces  machinery  has  been  installed  in 
several  leading  works.  Indeed,  since  the  decided  increase  in 
the  capacity  of  open-hearth  furnaces,  machine  charging  has 
become  imperative.  Large  furnaces,  mounted  on  circled 
supports,  and  which  can  be  tilted  either  to  receive  a  charge 
or  to  be  tapped,  are  in  successful  operation.  Plant  has  also 
been  installed  for  teeming  from  the  ladle  to  the  ingot  moulds 
in  a  separate  part  of  the  work.  Overhead  cranes  form  an 
important  part  of  that  and  some  other  arrangements. 

Modern  charging  machines  are  described  on  page  256. 


116 


CHAPTER    XL 
THE   ACID   OPEN-HEARTH   PROCESS. 

As  already  indicated.  Siemens,  or  Siemens-Martin,  steel  is 
made  in  large  reverberatory  furnaces  with  regenerators,  and 
gas  is  supplied  for  fuel. 

Working  an  Acid  Open -hearth  Charge.* — The  furnace 
being  in  good  working  condition  and  the  taphole  having  been 
made  up,  the  charge  of  pig  iron  and  scrap  is  put  in  either  by 
hand  or  by  machinery. 

To  charge  by  hand  a  piece  of  old  rail  is  laid  on  the  sill  or 
foreplate  at  one  of  the  charging  doors,  and  the  flat  part  of 
a  mild  steel  peel  (fig.  47)  is  set  on  it.  A  piece  t  of  hematite 


Fig.  47.— Peel,  Rail,  and  Foreplate. 

pig  iron  is  placed  on  the  peel,  the  door  is  raised,  the  peel 
is  pushed  into  the  furnace  and  turned  over  or  jerked  so  as  to 
drop  the  pig  iron  into  the  furnace.  The  peel  is  quickly  with- 
drawn, another  piece  of  pig  iron  is  placed  on  it  (fig.  48),  and 
is  quickly  charged  in  like  manner.  The  parts  of  the  working 

*  The  first  charge  in  a  new  furnace,  or  a  furnace  which  has  been 
"off"  for  repairs,  does  not  carry  as  heavy  a  tonnage  as  following 
charges.  The  second  and  third  charges  are  heavier,  and  at  the  fourth 
the  full  amount  may  be  charged  and  worked. 

t  For  convenience  of  charging,  the  "  pigs"  of  iron  are  broken  across 
into  two  parts. 


THE    ACID    OPEN-HFARTH    PROCESS.  117 

bed  of  the  furnace  furthest  from  the  doors  being  thus  charged, 
and  the  pig  iron  well  placed  at  the  sides  and  back  of  the 
working  bed,  the  remainder  of  the  pig  iron  is  thrown  in. 
Steel  scrap  is  similarly  charged  over  the  top  of  the  pig 
iron.* 

When  charging  is  completed  the  doors  are  closed  (they  are 
kept  closed  as  much  as  possible  during  charging),  the  valves 
are  reversed  from  time  to  time,  and  the  charge  in  the 
furnace  molts 


Fig.  48.  —Men  Charging  Steel  Furnace. 

Oxidation  steadily  proceeds.  In  the  first  two  stages  the 
oxidation  is  effected  by  the  excess  air  which  enters  the  furnace 
along  with  the  producer  gas.  To  bring  on  the  "  boil,"  ore 
is  charged  towards  the  end.  The,  oxidised  products — silica 
(Si02),  oxide  of  manganese  (MnO),  and  some  oxides  of  iron 
(FeO  and  Fe203) — go  into  the  slag.  In  the  third  stage  oxida- 
tion is  largely  due  to  the  oxygen  in  the  ore  which  is  fed  in. 
When  the  charge  has  become  sufficiently  decarburised,  and  the 
bath  of  metal  is  in  good  position  for  tapping,  the  taphole  is 

*  Instead  of  charging  cold  pig  iron  into  the  furnace,  much  fluid  metal 
is  now  used  in  some  works. 


118  IRON    AND   STEEL    MANUFACTURE. 

opened — as  described  on  p.  115 — and  the  metal  flows  from 
the  furnace  along  the  spout  and  launder  into  the  hot  ladle 
(fig.  49)  which  is  ready  to  receive  it. 

On  tapping  the  furnace  the  "  metal "  comes  first,  then  metal 
and  slag,  then  mostly  slag.  When  nearly  all  the  steel  has 
gone  into  the  ladle,  the  launder  (see  fig.  42)  is  struck  a  heavy 
blow  with  a  sledge  hammer,  thus  separating  the  two  parts. 
The  slag,  with  a  little  of  the  metal,  is  thereby  diverted  to  th« 
slag  tub  beneath.  When  the  ball  of  slag  has  solidified  it  is 


Fig.  49. — Steel  and  Slag  being  Tapped  from  Furnace. 

emptied  out  of  its  tub,  and  any  metal  which  may  have  been 
with  it  is  collected. 

In  some  works  all  the  slag  is  run  into  the  ladle,  some 
of  the  slag  being  allowed  to  overflow  into  the  adjoining  slag 
tub.  In  such  cases  practically  the  whole  of  the  steel  goes  into 
the  ingot  moulds.  It  is  a  good  plan ;  more  ingot  steel  is 
,  and  less  scrap  steel ;  besides,  the  slag  left  on  the  top 


THE    ACID    OPEN-HEARTH    PROCESS.  119 

keeps  the  steel  warm  while  casting  is  going  on.     But   this 
plan  involves  the  use  of  very  large  ladles. 

When  about  one-third  of  the  metal  has  entered  the  ladle 
a  weighed  quantity  of  hot  ferro-manganese,  in  small  pieces,  is 
shovelled  into  the  ladle  to  act  as  a  deoxidiser  and  to  provide 
a  small  percentage  of  manganese,  which  acts  beneficially  in 
the  steel.  The  "  addition  "  is  generally  completed  when  the 


Fig.  50.— Teeming  Steel  into  Ingot  Moulds. 

second-third  has  run  into  the  ladle.  It  soon  melts,  and  the 
churning  up,  due  to  the  fall  of  the  remainder  of  the  metal  into 
the  ladle,  causes  the  ferro-manganese  to  become  so  diffused 
that  a  fairly  homogeneous  steel,  containing  a  definite  per- 
centage of  carbon  and  manganese,  is  produced. 

If,  instead  of  mild  steel,  a  medium  steel  (say  a  steel  with 
0-5  per  cent,  of  carbon)  is  required,  a  weighed  quantity  of  hot 


120  IRON    AND    STEEL    MANUFACTURE. 

spiegel-eisen  is  added,  and  allowed  to  melt  and  mix  through 
the  bath  of  metal  before  tapping  the  furnace.  Ferro-manganese 
is  also  added  in  the  ladle.  Spiegel-eisen  is  not  used  in  the 
manufacture  of  mild  steel. 

The  steel  in  the  ladle  is  discharged  through  the  nozzle  into 
the  moulds  in  the  manner  described  in  connection  with  the 
Bessemer  process,  and  shown  in  fig.  50.  When  the  ingot  has 
set,  the  mould  is  stripped  off  (see  fig.  51),  and  the  ingot  is 


Fig.  51.— Stripping  Steel  Ingot. 

removed  for  reheating  or  to  be  stocked.  The  peculiarities  of 
a  steel  ingot  and  the  further  treatment  to  which  it  is  subjected 
are  dealt  with  in  Chapter  xiii. 

On  the  completion  of  the  teeming,  the  ladle  is  wheeled  to 
a  convenient  part  of  the  casting  pit,  turned  over  to  get  rid  of 
the  remaining  slag  (fig.  52),  and  the  nozzle  is  knocked  out  to 
be  ready  for  the  fitting  in  of  a  new  one. 

Composition  of  the  Materials  used  in  the  Open-hearth 
Process. — The  pig  iron  is  of  the  kind  known  in  the  trade  as 


THE    ACID    OPEN-HEARTH    PROCESS. 


121 


Bessemer  pig  iron,  or  hematite  pig  iron,  the  composition  of 
which  is  noted  below.     The  steel  scrap  charged  has,  of  course, 


Fig.  52.— Empty  Steel  Ladle. 

the    composition    of   the   finished   steel,  which   is   also   noted 
below  : — 


Constituents. 

Chemical 
Symbols. 

Hematite 
Pig  Iron. 

Steel  Scrap. 

jCarbon  (graphitic), 

c 

3-500 

None. 

Carbon  (combined),     . 

c 

0-250 

0-170 

Silicon,        .... 

Si 

2-200 

0-025 

Sulphur,      .... 

s 

0-047 

0-049 

Phosphorus, 

p 

0-047 

0-050 

Manganese, 

Mn 

0-500 

0-500 

Iron  (by  difference),   . 

Fe 

93-464 

99-215 

100-000 

100-000 

The  finishing  materials  (ferro-manganese  and  spiegel-eisen) 
are  similar  to  those  used  for  the  Bessemer  process.  Their 
composition  is  noted  on  p.  237. 

Good  Campanil  Ore,  a  favourite  brown  hematite  for  the 
process,  approximates  in  composition  to  the  following : — 


122 


IRON    AND    STEEL    MANUFACTURE. 


Constituents. 

Chemical 
Formulae. 

Percentage. 

Ferric  oxide,  . 
Manganic  oxide,    . 
Silica,    . 

Fe203 
Mn304 
Si02 
CaO 

75-0 
1-0 

6-0 
4-50 

Magnesia, 
Phosphoric  acid,    . 
Carbon  dioxide,     . 
Water  (combined), 

MgO 

PA 

CO., 
H26 
HO 

1-50 
0-03 

4-8 
4-0 
3-0 

99-83 

Metallic  iron,         .... 

Fe 

52-5 

The  carbon  dioxide  and  combined  water  are  soon  driven  off 
at  the  temperature  of  the  furnace.  The  ore  thus  becomes 
porous — a  good  condition  for  being  rapidly  reduced. 


Chemical  Considerations. 

During  the  first  stage  of  the  process — the  melting  down 
stage — about  one-half  of  the  silicon  and  about  one-third  of 
the  manganese  in  the  charge  are  oxidised.  The  oxides, 
uniting  with  oxidised  iron,  form  slag.  A  little  of  the  carbon 
may  be  oxidised  and  escape  in  the  outgoing  gases. 

During  the  second  stage — going  on  the  boil — the  remainder 
of  the  silicon  and  manganese  are  eliminated,  and  there  is  a 
noticeable  diminution  in  the  amount  of  carbon  left  in  the 
charge. 

During  the  third,  or  boiling  stage,  more  carbon  is  oxidised, 
and,  as  the  carbon-with-oxygen  compounds  (carbon  monoxide 
and  carbon  dioxide)  are  gaseous,  they  cause  a  commotion, 
with  appearance  of  boiling,  as  they  come  off.  When  this 
stage  is  reached  good,  pure,  lumpy  hematite  ore  (preferably 
Campanil  ore)  is  cautiously  fed  into  the  furnace.  The  chief 
constituent  of  the  ore  is  ferric  oxide  (Fe2O3),  which,  in  the 
furnace,  is  decomposed ;  its  oxygen  hastens  the  burning  out 
of  the  carbon,  and  the  iron  which  is  reduced  increases  the 


TUB    ACID    OPEN-HEARTH    PROCESS.  123 

weight  of  ingots  produced.  A  double  duty  is  thus  done— 
the  carbon  of  the  pig  iron  is  oxidised  and  eliminated,  and 
iron  is  produced  direct  from  the  ore. 

If  too  much  ore  is  fed  in,  or  if  it  is  fed  too  quickly,  the 
steel  is  apt  to  be  "  wild,"  unmanageable,  and  unsound. 

The  chemical  reactions  are  the  same  as  in  the  acid 
Bessemer  process,  as  detailed  on  pp.  78  and  79,  but  in  the 
open-hearth  process  the  oxidation  of  the  carbon  is  chiefly 
effected  by  oxygen  from  ferric  oxide  (in  the  ore  used),  as 
indicated  by  the  equation — 

3C          +          Fe203  =        2Fe       +  SCO 

Carbon    and    ferric  oxide    yield    iron    and     carbon  monoxide. 

Carbon  dioxide  (C02)  is  also  produced. 

The  gases,  carbon  monoxide  or  carbon  dioxide,  as  the  case 
may  be,  escape  with  the  outgoing  gases  from  the  furnace. 
The  other  oxidised  materials  go  into  the  slag. 

Action   of  the    Ferro-Manganese   or   Spiegel-eisen. — The 

deoxidising  action  of  the  manganese  is  the  same  as  in  the 
Bessemer  process  (see  p.  79);  but  in  the  Bessemer  process 
the  metal  is  completely  deearburised  before  the  spiegel-eisen 
or  ferro-manganese  are  added.  In  the  open-hearth  process  the 
"metal"  which  is  ready  for  tapping  contains  carbon.  In 
deciding  on  the  material  necessary  for  deoxidising  open-hearth 
steel,  allowance  must  be  made  for  the  carbon  contained  in  the 
ferro-manganese  or  spiegel-eisen.  In  deoxidising  Bessemer 
metal,  carbon  must  be  added  to  carbonise  the  metal :  in  finish- 
ing open-hearth  steel,  the  carbon  which  is  unavoidably  present 
in  the  deoxidising  materials  must  be  allowed  for,  and  the  open- 
hearth  metal  deearburised  to  the  proper  percentage  before 
being  tapped.  Thus,  for  a  charge  of  finished  steel  to  contain 
a  half  per  cent.  ('50)  of  carbon,  the  bath  of  metal  in  a  furnace 
will  be  held  to  be  sufficiently  deearburised  when  -37  per  cent.* 
of  carbon  is  present.  If  at  this  stage  the  other  indications 
give  assurance  that  the  metal  is  ready  for  finishing  and 
tapping,  the  right  quantity  of  hot  spiegel-eisen  will  be  thrown 
in.  There  are  unmistakable  signs  known  to  good  steel 
*  The  steel  melters  would  call  this  37  points. 


124  IRON    AND    STEEL   MANUFACTURE. 

smelters.  If,  for  instance,  the  slag  which  clings  to  the  handle 
of  a  sample  spoon  or  other  tool  breaks  off  in  a  clean,  crisp 
manner  when  thrown  down,  the  "first  hand" — taking  into 
account,  of  course,  other  considerations— will  correctly  con- 
clude that  the  charge  is  in  good  condition  for  tapping.  The 
fracture  of  the  small  test  button — which  is  obtained  by  taking 
out  a  sample,  partly  cooling  it,  hammering  it  flat,  breaking  it 
across,  and  examining  the  appearance  of  the  fracture — its 
soundness  and  malleability  (or  the  absence  of  these  qualities) 
afford  valuable  guidance. 

Before  finishing  a  charge  it  is  generally  good  practice  to 
"  pig  back " — that  is,  to  place  a  few  half  pigs  of  good  rich 
grey  hematite  iron  (hematite  pig  iron  containing  much  carbon 
and  silicon)  just  inside  the  doors  of  the  furnace,  and,  when  the 
pig  iron  is  red-hot,  to  push  the  pieces  into  the  bath  and  rabble 
vigorously.  The  result  of  this  is  most  beneficial,  as  the  silicon 
"  kills  "  some  of  the  active  oxides  which  may  remain.  A  quiet 
metal  may  thus  be  ensured.  The  unfinished  steel  may  then 
receive  the  addition  of  spiegel-eisen,  if  a  medium  steel  is 
required,  or  be  tapped  and  treated  with  ferro-manganese  in 
the  ladle  if  mild  steel  is  wanted. 

Before  tapping,  it  is  essential  to  success  that  the  metal  and 
the  slag  should  both  be  in  good  condition.  The  metal  should 
be  hot  enough  to  undergo  the  natural  cooling  in  the  ladle 
before  and  during  pouring  into  the  several  moulds — with,  of 
course,  a  margin  of  safety.  But  it  is  well  that  the  steel 
should  not  be  too  hot  when  teemed. 

The  proportion  of  pig  iron  and  scrap  steel  in  a  charge  will 
depend  on  circumstances.  As  steel  cannot  be  worked  without 
the  production  of  scrap  it  is  necessary  to  have  a  process  in 
which  it  can  be  utilised.  Where  scrap  is  plentiful,  as  much  as 
80  per  cent,  may  be  charged,  and  with  such  a  proportion  the 
charge  can  be  worked  through  quickly.  On  the  other  hand, 
charges  containing  75  per  cent,  of  pig  iron  are  regularly 
worked.  Scrap  steel  is  not  necessary  for  the  process.  Some- 
times it  is  convenient  to  work  with  about  equal  quantities  of 
pig  iron  and  scrap  steel,  and  such  a  charge  might  be  made  up 
of  the  following  for  each  10  tons: — 


THE    ACID   OPEN-HEARTH    PROCESS. 


125 


6  tons  of  hematite  pig  iron  (of  various  brands*), 
4  tons  of  scrap  steel. 

1£  tons  of  brown  hematite  ore  will  be  used  for  feeding,  and 

about 

2  cwts.  of  ferro-manganese  may  be  required  for  deoxidising, 
and  yielding  the  required  manganese. 

The  progress  of  the  process  may  be  traced  from  the  following 
figures : — 


Composi- 
tion of  the 
Pig  Iron 
and  Scrap 
Steel  as 
Charged. 

Composi- 
tion when 
Melted. 

Composi- 
tion at  the 
Beginning 
of  the  Boil. 

Composi- 
tion when 
ready  for 
the  Ferro 
or  Spiegel. 

Composi- 
tion of  the 
Finished 
Mild 
Steel. 

Carbon, 
Silicon, 
Phosphorus, 
Sulphur, 
Manganese, 
Iron,     . 

2-85 
1-41 
0-048 
0-048 
0-75 
A 

2-63 
0-84 
0-048 
0-048 
0-56 
A 

2-50 
0-36 
0-049 
0-049 

0-11 

A 

0-13 
0-02 
0-049 
0-050 
Trace. 
A 

0-18t 
0-02 
0-05 
0-05 
0-54 
A 

100-000 

100-000 

100-000 

100-000 

100-000 

1 

The  increase  in  the  percentage  of  phosphorus  is  due  to  its 
being  concentrated  in  less  weight  of  "  metal "  up  to  the  time 
of  boiling,  for,  in  addition  to  the  elimination  of  carbon,  silicon, 
and  manganese,  some  iron  will  have  become  oxidised,  and,  as 
oxide,  removed  to  the  slag.  As  the  ore  which  is  fed  in 
becomes  reduced  the  weight  of  "  metal "  increases,  but  as  the 
ore  contains  phosphoric  acid  (P205),  which  is  reduced  to 
phosphorus,  the  percentage  in  the  metal  is  not  diminished 
thereby.  A  slight  increase  in  the  percentage  takes  place  on 
the  addition  of  ferro-manganese,  which  is  due  to  phosphorus 
in  that  material. 

*  Where  pig  iron  is  purchased,  a  variety  of  brands — each  with  the 
distinctive  mark  of  the  maker— is  prepared  for  each  charge.  Steel- 
makers who  produce  pig  iron  use  their  own  make. 

fThe  carbon  is  purposely  varied  to  suit  requirements,  the  other 
elements  are  fairly  constant  in  percentage. 

A  By  difference. 


126 


IRON    AND    STEEL    MANUFACTURE. 


The  same  remarks  apply,  in  some  measure,  to  the  increase 
in  the  percentage  of  sulphur.  And  the  melted  metal  some- 
times takes  up  sulphur  from  the  producer  gas  which  is  burnt 
in  the  furnace.  By  careful  boiling  of  the  charge  it  is  possible 
to  diminish  the  amount  of  absorbed  sulphur. 

The  Slag  produced  may  be  composed  of  the  following,  in 
proportions  near  to  the  figures  given : — 


Constituents. 

Chemical 
Formulae. 

Approximate 
Percentage. 

Silica,    

SiO« 

56 

Alumina,        
Ferrous  oxide,        .... 
Manganous  oxide,  .... 

fifr 

MnO 
CaO 

1 

27 
10 
5 

MgO,  &c. 

1 

100 

Although  such  slag  contains  21  per  cent,  of  iron  and  7 '75 
per  cent,  of  manganese,  no  process  is  at  work  for  utilising  more 
than  a  very  small  amount  of  the  enormous  quantity  which  is 
regularly  produced. 


127 


CHAPTER  XII. 
THE  BASIC  OPEN-HEARTH  PROCESS. 

THE  production  of  trustworthy  steel  from  materials  which 
contain  phosphorus  in  medium  amount  has  been  forced  on  the 
trade.  The  process  has  assumed  large  proportions  and  is 
growing  in  importance.  The  elimination  of  phosphorus  from 
melted  pig  iron  having  been  successfully  carried  on  in  a  basic- 
lined  Bessemer  converter,  attempts  to  dephosphorise  in  an 
open-hearth  furnace  became  inevitable.  Open-hearth  steel  is 
popular  with  many  purchasers. 

The  advantages  of  working  in  a  reverberatory  furnace 
have  already  been  stated,  see  p.  14.  To  the  advantages 
previously  mentioned  may  be  added  this  important  one, 
namely  : — That  as  the  temperature  is  maintained  by  burning 
the  gas  supplied  for  heat  raising,  it  is  not  necessary,  as  in 
the  basic  Bessemer  process,  to  have  a  large  percentage  of 
phosphorus  to  keep  up  the  heat  by  its  oxidation. 

Many  ores  yield  pig  iron  containing  a  medium  quantity  of 
phosphorus — too  high  to  be  dealt  with  in  an  acid-lined  furnace, 
or  acid-lined  converter,  and  not  high  enough  to  yield  heat 
sufficient  for  Bessemerising.  And  even  from  pig  iron  obtained 
from  good  ores  comparatively  low  in  phosphorus,  some  of  that 
deleterious  element  can  be  eliminated  and  a  superior  quality 
of  soft  steel  obtained. 

Until  the  advent  of  the  basic  open-hearth  process  such 
ores  were  almost  valueless  for  steel  -  making.  A  famous 
American  iron-master  bought  extensive  mines  of  medium 
phosphoric  ore  for  a  modest  sum.  By  the  successful  working 
of  the  basic  open-hearth  process  these  ores  attained  a  high 
commercial  value. 

The  furnace  requires  a  basic  lining,  for  reasons  stated  on 
p.  84,  and  the  basic  lining  is  the  only  matter  in  which  the 
plant  differs  from  the  original  open-hearth,  or,  as  it  is  now 
called,  the  acid  Siemens  process ;  except  that,  as  a  greater 
quantity  of  slag  is  produced  in  the  basic  than  in  the  acid 


128  IRON   AND    STEEL   MANUFACTURE. 

process,  smaller  charges  of  basic  steel  must  be  worked  in 
furnaces  of  given  capacity. 

The  same  style  of  valves,  cranes,  ladles,  moulds,  &c.,  are 
used  as  for  the  acid  open-hearth  process. 

The  furnace  bottom  is  of  cast-iron  plates  carried  on  steel 
bearers.  Bricks,  preferably  of  a  neutral  nature,  are  laid  over 
the  cast-iron  plates  and  the  bricks  are  covered  with  a  thick 
basic  lining  of  burnt  magnesite  or  burnt  dolomite  and  hot, 
boiled,  anhydrous  tar.  The  basic  lining  may  be  put  in 
in  one  of  three  ways  : — 

(a)  It  may  be  spread  and  pressed  with  hot  rammers,  in 
the  manner  described  when  dealing  with  the  lining 
of  a  basic  converter. 

(5)  It  may  be  made  up  of  pressed  bricks  cemented  together 
and  covered  over  with  rammed  basic  material. 

(c)  It  may  be  spread  and  heated  so  that  the  materials  fuse 
together,  one  thin  layer  being  run  on  the  top  of  an- 
other in  the  same  manner  as  a  sand  lining  is  put  in 
an  open -hearth  furnace. 

A  good  method  of  lining  a  basic  open-hearth  furnace  is  to 
set  a  course  of  firebricks  on  the  iron  plates  and  a  layer  of 
magnesia  bricks  thereon,  then  "  burn  in  "  a  coating  of  burnt 
dolomite  mixed  with  5  per  cent,  of  finely-ground  basic  slag, 
each  layer  being  firmly  bound  together  by  heat.  When  the 
"burning  in"  is  finished,  ground  basic  slag  is  thrown  on  the 
banks,  where  it  melts  and  is  absorbed.  This  is  continued  till 
a  pool  of  melted  slag  is  found  on  the  bottom. 

It  is  a  safe  plan  to  finish  the  bottom  by  ramming,  and 
then  heat  the  furnace  with  gas  for  at  least  a  week  before 
commencing  to  charge. 

A  magnesia  lining  formed  of  thoroughly  calcined  magnesite, 
cemented  with  magnesium  chloride,  is  highly  recommended. 

As  chemical  action  would  take  place  between  the  acid 
bricks,  of  which  the  furnace  walls  are  built  up,  and  the  basic 
lining,  it  is  usual  to  form  a  neutral  course  where  the  thin  part 
of  the  lining  rests  on  the  brickwork  as  shown  in  fig.  53. 
The  neutral  course  may  consist  of  a  mixture  of  crushed 


THE    BASIC    OPEN-HEARTH    PROCESS. 


129 


Fig.  53.— Neutral  Rib,  B,  dividing  Silica 
Bricks,  A,  from  Dolomite  Lining,  0. 


chrome  iron  ore  and  tar  rammed  in  position,  or  of  neutral  bricks 
(made  of  chrome  iron  ore  mixed  with  tar,  pressed  and  kiln- 
fired)  carefully  built  in 
the  course.     It   is   not 
unusual   to   have  mag- 
nesia  brick  walls  below 
the  line  of  the  neutral 
rib. 

The  mixture  used  for 
ramming  the  taphole  is 
calcined  dolomite,  with 
tar  and  anthracite. 

The  Materials  used 
in  the  Process  are  pig 
iron,  broken  iron  cast- 
ings, scrap  steel,  scrap  wrought  iron,  iron  cinders  which  do 
not  contain  too  much  silica,  calcined  pottery  mine,  purple  ore, 
impure  hematite  ore,  and  limestone — both  raw  and  calcined. 
The  charge  is  finished  with  ferro-manganese  in  the  usual  way. 

The  Composition  of  the  Pig  Iron  used  varies  considerably, 
the  process  being  capable  of  utilising  pig  irons,  &c.,  having 
a  wide  range  of  composition.  Suitable  pig  iron  is  low  in 
silicon  and  in  sulphur.  The  content  of  phosphorus  is  not  of 
so  much  consequence  as  in  the  Bessemer  process ;  if  high,  a 
richer  slag  is  produced,  which  sells  at  a  higher  price,  but  the 
risks  in  working  are  greater,  and  more  time  is  occupied  in 
working  a  charge. 

The  following  may  be  taken  as  fairly  representative  of 
average  pig  iron  for  use  in  the  process  : — 


Constituent. 

Symbol. 

Percentage. 

Carbon,  

c 

About     3  '50 

Si 

1-00 

Phosphorus,  

P 

2-00 

Sulphur,         ..... 
Manganese,    

s 

Mn 
Fe 

0-06 
„         1-50 

A 

100-00 

130  IRON    AND    STEEL    MANUFACTURE. 

Pig  irons  containing  over  3  per  cent,  of  phosphorus  are 
regularly  worked. 

Working  a  Basic  Open-hearth  Charge. — When  the  furnace 
has  been  brought  into  good  working  condition,  the  scrap  is 
charged,  then  lime,  and  perhaps  some  ore,  and,  lastly,  the  pig 
iron.  In  due  course  the  charge  melts,  and  calcined  pottery 
mine  or  good  cinder  is  fed  into  the  furnace  to  hasten 


Fig.  54. — Shovelling  Lime  into  a  Steel-Melting  Furnace. 

oxidation,  and  lime  and  limestone  are  also  added  to  keep  the 
slag  in  good  basic  condition.  Elimination  of  silicon,  phos- 
phorus, sulphur,  and  carbon  proceeds  steadily.  From  time  to 
time  samples  of  the  "  metal "  are  taken,  and  quickly  tested. 
When  it  is  found  to  be  pure  enough,  it  is  tapped  out,  received 
in  a  hot  Bessemer  ladle,  deoxidised  with  ferro-manganese,  and 
discharged  into  the  ingot  moulds. 

If  the  pig  iron  is  high  in  sulphur,  3J  cwts.  of  limestone  and 
1^  cwts.  of  cinder  rich  in  iron  oxide  are  charged  per  ton  of 
metal.  This  yields  a  very  thick  slag,  which  is  opened  out 
with  3  or  4  cwts.  of  calcium  chloride  or  fluorspar  and  5  or  6 
cwts.  of  mill  scale  containing  not  more  than  8  per  cent,  of 


THE    BASIC    OPEN-HEARTH    PROCESS.  131 

silica.  If  the  slag  is  kept  in  proper  condition,  so  as  not 
to  eliminate  the  carbon  too  quickly,  the  sulphur  may  be 
diminished  in  quantity  and  brought  down  to  a  low  percentage. 

The  working  of  Cleveland  pig  iron  into  good  steel  in  basic 
open-hearth  furnaces  was  ably  pioneered  by  Mr.  E.  H.  Saniter. 

Mr.  G.  A.  Wilson  gives  details*  of  a  charge  containing 
1  per  cent,  of  silicon,  0*2  per  cent,  of  sulphur,  and  V5  per 
cent,  of  phosphorus  being  so  worked  as  to  produce  a  finished 
steel  containing  carbon  0'16,  silicon  0'004,  manganese  0'44, 
sulphur  0'042,  and  phosphorus  0'019  per  cent. 

Chemical  Considerations. — The  rate  at  which  the  elements 
are  eliminated  depends  on  the  composition  of  the  "  metal  "  and 
slag  and  the  conditions  of  working.  Speaking  generally,  silicon 
is  removed  early,  and  manganese  is  also  rapidly  removed.  This 
is  fortunate,  as  the  excess  oxide  of  manganese  formed  neutral- 
ises the  acid  nature  of  the  silica  which  is  formed  by  the 
oxidation  of  the  silicon.  The  carbon  and  the  phosphorus  are 
both  steadily  oxidised  and  removed  throughout  the  process. 
It  is  important  that  all  the  carbon  should  not  be  removed 
before  the  phosphorus,  as  the  commotion  caused  by  the 
elimination  of  carbon  (as  gas)  aids  in  quickly  bringing  the 
metal  into  more  intimate  contact  with  the  slag  from  which, 
especially  towards  the  finish,  the  oxidation  is  derived,  and 
the  lime  of  which  takes  up  the  phosphoric  acid. 

A  slag  which  is  too  rich  in  iron  oxides  or  is  not  of  the 
right  consistency  may  give  rise  to  trouble  in  working  the 
charge.  Insufficiency  of  lime  in  the  slag  may  cause  a  charge 
to  go  "off  the  boil"  before  enough  phosphorus  has  been 
eliminated.  In  such  a  case,  more  lime  is  added  and  hot  pig 
iron  is  charged  in  order  to  renew  the  "boiling,"  so  that  a 
steel  containing  only  a  small  quantity  of  phosphorus  may  be 
produced. 

The  composition  of  the  finished  steel  is  much  the  same  as 
that  of  acid  open -hearth  steel.  Basic  steel  is,  however, 
frequently  lower  in  phosphorus.  The  percentage  of  carbon  is 
varied  as  required. 

*  West  of  Scotland  Iron  and  Steel  Institute  Journal,  Nov.  1903. 


132 


IRON    AND    STEEL    MANUFACTURE. 


The  (basic)  slag — which  contains  much  phosphoric  acid 
when  a  highly  phosphoric  pig  iron  is  used — is  collected,  and, 
if  rich  enough  in  phosphoric  acid,  is  ground  to  fine  powder, 
and  sold  for  manure.  If  poor,  it  is  tipped  on  the  slag  heap. 

The  slag  produced  when  fluorspar  is  used  is  not  as  soluble 
as  ordinary  basic  slag;  it  therefore  has  a  lower  agricultural 
value,  and  does  not  command  such  a  high  price. 

The  chief  points  of  difference  between  the  acid  and  the  basic 
open-hearth  processes  are  : — 


ACID. 
with 


siliceous 


Furnace     lined 

material. 
Taphole  rammed  with  anthracite 

and  sand. 

Hematite  pig  iron  used. 
Pure  scrap  used. 

Pure  quality  brown  hematite  ore 
used  for  feeding. 

No  elimination  of  phosphorus. 
Valueless  slag  produced. 


BASIC. 

Furnace  lined  with  basic  material. 

Taphole  rammed    with  calcined 

dolomite    and    tar,   and    some 

anthracite. 

Phosphoric  pig  iron  used. 
Phosphoric  scrap  may  be  used. 
Iron  ores  or  cinders  containing 

phosphorus  used    for  feeding. 

Lime  freely  used. 
Phosphorus  eliminated. 
Fertilising  slag  produced  and  sold, 


COMPOSITION    OP    STEELS. 


133 


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134 


CHAPTER     XIII. 
i 

BESSEMER   AND    SIEMENS    STEEL    INGOTS. 

As  stated  in  preceding  chapters,  ingot  moulds  are  suitably 
set  and  fluid  steel  is  poured  into  them. 

If  the  newly-teemed  steel  proves  to  be  "  fiery  "  or  "  wild  " 
— throwing  off  sparks  very  actively  and  frothing  or  boiling 
in  the  moulds — quietness  may  be  induced  by  throwing  little 
pieces  of  aluminium  into  the  steel.  The  effect  appears 
magical  and  out  of  all  proportion  to  the  small  amount  of 
aluminium  used.  Soundness  in  the  ingot  may  be  promoted 
by  the  judicious  addition  in  the  furnace  of  an  alloy  of  iron 
containing  much  silicon.  Alloys  such  as  silico-ferro  and  silico- 
spiegel  (see  analysis  on  p.  238)  may  be  used  in  small  amount. 

A  common  practice  for  promoting  soundness  is  that  of 
stoppering  the  ingot.  The  practice  is  this: — The  mould  is 
not  quite  filled  with  steel,  and  sand  is  thrown  into  the 
unoccupied  space ;  on  the  top  of  the  sand  a  rigid  metal  plate 
is  placed,  a  bar  is  thrust  through  the  two  lugs  of  the  mould 
and  a  wedge  is  firmly  driven  in  between  the  plate  and  the 
bar.  Ingots  stoppered  down  in  this  way  are  shown  in  fig.  50, 
p.  119. 

When  the  ingots  have  sufficiently  solidified,  on  the  out- 
side, so  that  the  crust  can  safely  contain  the  still  fluid 
interior  portion,  the  moulds  may  be  stripped  off  (see  fig.  51, 
p.  120),  the  covering  (if  any)  of  plate  and  sand  having  been 
previously  removed.  If  an  ingot  is  stripped  too  soon  a 
portion  of  the  crust  or  shell  may  give  way  and  steel  may  ooze 
or  flow  out — a  condition  known  in  works  as  "  bleeding." 
Such  ingots  are  objectionable.  Serious  accidents  have  arisen 
through  premature  stripping  of  ingots.  The  shrinking  of  the 
ingot  during  cooling  facilitates  stripping. 


BESSEMER    AND    SIEMENS    STEEL    INGOTS.  135 

To  remove  ingots  they  are  gripped  by  "  dogs  "  at  the  end 
of  a  crane  chain  (see  fig.  32,  p.  77)  and  conveyed  to  be 
brought  into  condition  for  rolling,  or  to  be  stocked  till 
required. 

The  moulds  are  cooled  either  by  natural  exposure  to  air, 
or,  more  quickly,  in  a  vat  or  by  a  spray  of  water.  The  latter 
method  is  not  economical.  They  are  re-set  as  required  for 
further  use. 

An  ingot  of  steel,  while  cooling,  becomes,  naturally,  solid 
on  the  outside  before  the  inside.  Impurities 
are  concentrated  in  the  portion  which  re- 
mains longest  in  the  fluid  state,  and  the 
more  slowly  an  ingot  cools  the  more  marked 
will  be  the  concentration,  or  segregation  as 
it  is  called,  of  impurities  in  the  centre. 

On  subjecting  drillings  from  the  longitu- 
dinal centre  of  an  ingot  to  chemical  analysis 
it  is  found  that  there  is  a  perceptibly  higher 
percentage  of  carbon,  phosphorus,  and  sul- 
phur than  in  drilling  from  parts  nearer  the 
sides  of  the  ingot.  This  is  fortunate,  for 
on  rolling  out  the  ingot  into  plates,  bars. 
&c.,  the  least  pure  portion  is,  and  remains, 
furthest  from  the  surface.  There  are  thus 
malleable  surfaces  and  a  harder  backbone 
in  cast  and  rolled  steel.  Fig  55>  _  sketch 

representing 

In   steel   works  practice  the  top  part  of      Vertical  Section 
an  ingot  is   cut  off   and  treated  as  scrap,     of  Partly -cooled 
because  it  is  unsound.      Why  so  1      There      Ingot, 
are  two  good  reasons. 

As  the  steel  ingot  cools  it  contracts,  and  contraction  goes 
on  smoothly  until  the  mass  has  become  partly  solid.  So  long 
as  the  steel  is  even  feebly  fluid  the  topmost  portion  settles 
down  comfortably  on  the  lower  parts  (fig.  55).  But,  in  course 
of  cooling,  the  outside  portion  of  the  upper  part — the  top,  and 
the  parts  next  the  ingot  mould — solidities,  while  the  still 


136  IRON    AND    STEEL   MANUFACTURE. 

liquid  centre  portion  flows  downwards  and  continues  to  make 
good  the  void  arising  from  the  gradual  cooling  and  contraction 
of  the  mid  and  bottom  parts.  A  hollow,  or  pipe,  is  thus 
formed  in  the  centre  of  the  top  part,  as  indicated  in  fig.  55. 
This  piping  is  well  marked  in  good  crucible  steel  ingots. 

And  there  is  another  serious  imperfection  in  the  top  part. 
This  arises  from  the  comparatively  slow  expulsion  of  gases 
from  the  cooling  ingot.  The  retaining  of  gases  in  fluid,  and 
even  solid,  steel  is  remarkable.  We  speak  of  occluded  gases 
and  of  occlusion — that  is,  of  gases  which  are  naturally  retained 
in  liquid  metals,  and  sometimes  for  a  considerable  time  in 
solid  metals.  As  a  steel  ingot  cools  down,  and  becomes  more 
solid  and  dense,  some  of  the  gases  are,  as  it  were,  squeezed 
out,  and  ascend  through  the  still  liquid  upper  parts  of  the 
mass.  But  the  topmost  part  solidifies  before  the  whole  of 
the  middle  and  lower  parts,  and  thus  a  crust  is  formed  which 
the  ascending  gases  are  unable  to  get  through.  The  gases 
which  are  thus  trapped  often  gather  into  globules,  and  exert 
such  a  pressure  as  to  force  a  part  of  the  solidified  top  slightly 
upwards.  The  cavities  so  formed  in  the  steel  are  known  as 
blowholes.*  These  blowholes  naturally  accumulate  near  the 
top,  and  render  that  portion  unreliable  (see  fig.  55).  Hence 
the  trade  practice  of  cutting  off  the  top  part  and  treating  it 
as  scrap. 

The  advantages  of  pressing  a  newly-teemed  ingot  with 
a  layer  of  sand  and  firmly  covering  with  a  wedged-down  steel 
plate  should  be  plainly  apparent.  The  top  part  does  not  then 
solidify  as  quickly  as  when  exposed  to  the  air ;  the  ascending 
gases  are  thus  allowed  more  time  to  escape  through  the  fluid 
steel  at  the  top.  Without  difficulty  the  gases  which  rise 
clear  of  the  steel  find  an  exit  between  the  sand  granules  and 
past  the  edges  of  the  plate.  Later,  the  top  part  cannot  be  so 
easily  raised  by  the  gases,  and  so  the  ingot  is  left  in  a  more 
solid  condition. 

A  sample  of  Bessemer  steel  was  found  to  have  occluded 
seventy  times  its  own  bulk  of  gases.  On  withdrawing  the 

*  The  escape,  or  non-escape,  of  the  gases  from  a  cooling  ingot  have 
some  resemblance  to  the  "  working"  of  a  piece  of  dough.  Sometimes  a 
bubble  bursts  through  the  dough,  but  the  dough  being  in  the  plastic 
condition,  the  opening  is  soon  closed.  Much  of  the  gas,  however, 
cannot  escape,  hence  the  open  structure  of  bread. 


BESSEMER    AND    SIEMENS    STEEL    INGOTS. 


137 


gases  the  steel  was  to  all  appearance  quite  solid.     Occluded 
gases  are  slowly  given  off  from  cold  steel. 

The  composition  of  the  gaseous  mixture  occluded  in  solid 
steel  must  vary  very  much.  The  following  may  be  accepted 
as  approximately  representing  average  composition  : — 

Carbon  dioxide,         ...       2  per  cent. 
Carbon  monoxide,     .         .         .55       „ 
Hydrogen,  &c.,          .         .         .     43       ,. 

The  large  percentage  (98)  of  reducing  gases  is  important. 

Treatment  of  Ingots  before  Rolling. — The  ingots  produced 
by  either  of  the  Bessemer  or  Siemens  processes  require  to  be 


Fig.  56. — Reheating  Furnace— Longitudinal  Section. 

H,  Fire-bridge. 

J,    Coal-firing  door. 

K,  Iron  bearers. 


A,  Stack. 

B,  Buckstave. 

C,  Plates. 


D,  Tie-rod. 

E,  Roof  (brickwork). 

F,  Door. 


reheated,  or  have  their  heat  equalised,  before  being  rolled  into 
useful  forms.  An  ingot,  as  previously  stated,  naturally  cools 
more  quickly  on  its  outside  than  in  its  interior.  As  soon  as 
the  outside  has  solidified  sufficiently,  or  as  soon  as  a  thick 
enough  crust  or  shell  has  formed,  the  mould  is  stripped  off  the 
ingot  and  is  laid  aside.  The  ingot  (which  is  then  red  hot  on 
the  outside  and  white  hot  and  quite  fluid  within)  is  conveyed 


138  IRON    AND    STEEL    MANUFACTURE. 

to  a  reheating  furnace,*  or  to  a  soaking  pit,  or  a  vertical  re- 
heating furnace,  to  be  heated  uniformly  before  being  rolled 
or  hammered. 

An  ordinary  reheating  furnace  is  of  the  reverberatory 
type.  It  is  built  of  refractory  fireclay  bricks,  has  suspended 
doors,  and  is  very  much  like  a  puddling  furnace.  The  chief 
differences  are  that  the  reheating  furnace  has  no  flue-bridge, 
and  that  the  neck,  or  flue,  between  the  furnace  and  the 
chimney  is  arranged  so  as  to  form  a  slag  run  for  the  flue 
cinder  (fig.  56). 

Reheating  furnaces  are  worked  by  gas  or  by  a  coal  fire. 
One  district  favours  one  system,  while  another  district  adopts 
and  retains  the  other.  Doubtless  each  has  found  out  the  one 
best  adapted  to  its  requirements  and  suited  to  its  fuel. 

The  working  bottom  of  the  furnace  may  be  of  sand,  or  of 
iron  ore,  or  of  selected  basic  slag.  The  latter  was  patented 
by  Messrs.  Harbord  &  Tucker,  and  has  given  much  satisfaction 
in  steel  works. 

The  ingots  are  charged  horizontally  into  a  furnace,  and 
are  allowed  to  remain  there  until  each  has  attained  throughout 
its  mass  a  suitable  temperature  for  rolling. 

A  distinct  advance  in  steel-working  was  made  by  the  late 
Mr.  John  Gjers'  invention  of  the  soaking  pit. 

Soaking  Pits  are  arranged  in  sets.  They  are  built  in 
a  mass  of  brickwork  on  a  concrete  foundation.  Each  pit  has 
a  carefully  mitred  lining  of  fireclay  lumps  6  inches  thick  on  its 
four  sides.  A  good  hard  working  bottom  is  made  of  broken 
bricks  and  silver  sand.  At  the  top,  on  the  floor  level,  is 
a  frame  of  cast  iron,  and  the  working  doors  or  covers  consist 
of  iron  frames  enclosing  firebrick  slabs  These  covers  are 
lifted  and  replaced,  when  required,  by  cranes,  or  are  moved  by 
other  contrivances.  Each  pit  is  about  6  inches  deeper  and 
3  inches  wider  than  the  ingots  intended  to  be  dealt  with. 
Soaking  pits  are  worked  by  the  heat  remaining  in  the  hot 
ingots  which  are  charged  into  them. 

*  Occasionally  the  ingots  are  allowed  to  cool  down  completely,  and 
are  afterwards  reheated  and  rolled. 


BESSEMER    AND    SIEMENS    STEEL    INGOTS. 


139 


To  begin  with,  each  pit  is  warmed  by  a  succession  of  hot 
ingots  which  impart  heat  to  the  brickwork :  on  being  taken 
out  these  ingots  are  reheated  in  a  furnace.  The  pits,  having 
been  thus  heated,  are  ready  for  regular  working,  and  are 
charged  with  semi-cooled  ingots.  The  heat  of  the  steel  tends 
to  become  equalised  through  the  whole  ingot.  Little  heat 
escapes  from  the  pit,  and  much  is  absorbed  and  afterwards 
reflected  from  the  brickwork  on  to  the  ingot.  If  a  constant 


Fig.  57.—  Gjers'  Soaking  Pit. 


A,  Fireclay  cap  or  cover. 

B,  Brickwork. 

C,  Concrete  foundation. 

D,  Ingot. 

E,  Firebrick  lining. 


F,  Cast-iron  plates. 

G,  Cast-iron  plates  enclosing  F. 
H,  Cast-iron  brick-lined  cover. 
J,    Working  bottom. 


succession  of  hot  ingots  is  kept  up,  the  initial  heat  is  sufficient, 
by  equalising,  to  bring  the  whole  mass  of  the  metal  into  a  fit 
state  for  rolling. 

The  advantages  of  the  soaking  pit  are  : — 

(a)  Saving  of  fuel, 

(b)  The  ingots  are  handled  and  kept  in  a  vertical  position, 

(c)  The  four  sides  of  the  ingots  are  heated  equally,  and 

(d)  The  waste  of  iron  is  lessened. 


140 


IRON    AND    STEEL    MANUFACTURE. 


The  chief  drawbacks  are  the  awkwardness  of  the  preliminary 
heating  and  the  uncertainty  of  maintaining  a  constant  supply 
of  hot  ingots  from  the  casting  pits. 

It  is  now  usual  to  have  soaking  pits  coal-fired,  or  in  con- 
junction with  producers  which  supply  the  gas  for  heating  the 
pits  before  starting  and  when  empty.  They  are  therefore 
now  known  by  such  names  as  "  soaking  furnaces,"  "  vertical 
furnaces,"  &c.  Fig.  58  represents  half  of  a  series  of  soaking 
furnaces  which  are  gas-fired. 


Fig.  58. — Gas-fired  Soaking  Furnace — Longitudinal  Vertical  Section. 


A,  Floor  of  mild-steel  plates. 

B,  Air  regenerator. 

C,  Gas  regenerator. 

D,  Port. 


E,  Brick  arch. 

F,  Cover  of  soaking  chamber. 

G,  One  of  the  soaking  chambers. 


A  set  of  gas-fired  soaking  furnaces  consists  of  a  series  of 
firebrick-lined  cells  below  the  level  of  the  works  floor.  Deep 
archways  of  firebrick  support  the  covers,  and  from  these  a  large 
amount  of  heat  is  reflected.  This  keeps  the  top  part  of  the 
ingot  particularly  hot  and  thus  prolongs  the  fluid  and  plastic 
conditions  where  most  beneficial.  A  working  bottom  is  made 
up  as  in  the  original  soaking  pits,  and  tha  ingots  are  set  and 
kept  in  the  vertical  position  while  soaking.  At  the  lowest 
point  a  taphole  is  provided  through  which  slag  is  run  off. 


BESSEMER    AND    SIEMENS    STEEL    INGOTS.  141 

Producer  gas  is  provided  and  its  combustion  supplements 
the  heat  in  the  recently-stripped  ingots.  At  each  end  of  the 
series  of  pits  are  regenerators  for  gas  and  for  air.  The  pits 
are  worked  on  the  regenerative  system,*  and  the  flame,  in 
passing  from  one  end  to  the  other  (alternately  from  each  end), 
heats  the  ingot  with  fair  uniformity. 

From  a  furnace  which  is  sunk  in  the  ground  there  is  not 
much  loss  of  heat,  and,  as  the  current  passing  through  soaking 
furnaces  is  not  strong,  the  reducing  gases  from  the  ingots  are 
not  rapidly  carried  off.  The  "  atmosphere "  in  the  soaking 
furnace  is  therefore  not  so  strongly  oxidising  as  that  of  the 
ordinary  reverberatory  reheating  furnace,  f  and  hence  the  waste 
of  steel  is  not  so  great.  The  vertical  position  in  which  the 
ingot  is  set  for  soaking  is  preferable  to  the  horizontal  position. 
The  ingot  settles  more  solidly  and  all  sides  are  heated  alike. 

In  daily  works  practice,  the  ingots  are,  as  soon  as  per- 
missible (with,  of  course,  a  working  margin  of  safety),  con- 
veyed to  the  hot  cells  of  the  furnace  and  allowed  to  "  soak  " 
in  the  heat  thereof.  When  taken  out,  an  ingot  is  externally 
hotter  than  when  charged — its  heat  has  been  equalised 
throughout  its  mass. 

*  See  pp.  105  and  107  for  an  explanation  of  this  system. 

f  It  should  be  remembered  that  an  ordinary  reverberatory  furnace 
must  be  worked  with  an  excess  of  air  if  a  high  temperature  is  to  be 
maintained. 


CHAPTER   XIV. 
MECHANICAL  TESTING  OF  STEEL  AND  IRON. 

THE  fitness  of  finished  steel  and  iron  for  certain  purposes  is 
mechanically  tested  by  subjecting  prepared  test-pieces  to  a 
gradually  increasing  pull  or  stress  in  a  testing  machine,  noting 
the  tonnage  at  which  it  breaks,  and  measuring  the  extent  to 
which  it  has  stretched  and  the  reduction  in  area  of  the 
fractured  surfaces.  The  capacity  of  the  material  to  with- 
stand cracking  or  rupture  on  being  bent  or  flanged  is  some- 
times ascertained,  and  its  welding  quality  is  tried  on  certain 
occasions.  Resistance  to  impact  from  a  falling  weight  and 
other  tests  are  also  applied. 

Preparation   of  Test-Pieces. — A   selection   is   made  from 


Fig.  59a.— Flat  Test-piece,  before  Testing. 


Fig.  596.— Flat  Test-piece,  after  Testing. 

the  plates,  bars,  or  other  products  to  be  inspected,  and,  from 
portions  systematically  selected,  test-pieces  are  shaped  and 
marked. 

Strips  from  plates,  &c.,  are  cut  in  batches  to  the  shape  shown 
in  fig.  59a,  and  marks  are  punched  at  certain  distances — 
say  6,  cy,  or  10  inches  apart.  If  from  plates  J  inch  thick,  the 
strips  may  be  machined  so  that  the  narrowest  part  is  2  inches 
broad,  thus  giving  a  cross  area  of  1  inch.  In  all  cases  the 
rolled  surfaces  are  left  untouched,  the  machine  cutting  being 


MECHANICAL    TESTING    OP    STEEL    AND    IRON.  143 

done  on  the  edges  to  the    extent   necessary   to   bring   the 
breaking  stress  within  the  capacity  of  the  testing  machine. 

From  massive  pieces,  such  as  axles,  tyres,  &c.,  portions  are 
cut  out  and  turned  to  the  shape  shown  in  fig.  60a.  These 
when  finished  in  the  lathe  often  have  a  diameter  of  798  inch 
on  the  narrow  part :  this  gives  a  cross  area  of  '500224, 
or  a  mere  trifle  over  half  an  inch.  Wrought-iron  pieces  are 
often  turned  to  a  diameter  equal  to  1  square  inch.  Marks  are 
punched  at  certain  distances  apart.  In  preparing  test-pieces 
the  ends  are  left  broader  than  the  centre  portion:  this  ensures 
a  good  grip  when  in  the  testing  machine. 


Fig.  60a. — Cylindrical  Test-piece,  before  Testing. 


Fig.  607>. — Cylindrical  Test-piece,  after  Testing. 

Testing    the    Tensile''    Strength   of    a   Test-Piece. — The 

prepared  piece  having  been  securely  fixed  in  the  jaws  of  the 
testing  machine,  power  (generally  hydraulic)  is  applied  to 
pull  the  piece  till  the  stress  fractures  it.  The  amount  of 
stress  is  indicated  by  the  position  of  a  jockey  weight  which 
is  caused  to  travel  along  a  graduated  scale  on  a  beam.  If 
the  cross  area  of  a  test-piece,  before  being  fixed  in  the 
machine,  is  exactly  1  square  inch  (1  ID")  the  indicated  tonnage 
at  which  the  piece  was  ruptured  shows  directly  the  tensile 
strength  of  the  metal.  When  pieces  which  were  turned  to 
a  diameter  equal  to  J  a  square  inch  are  ruptured  the  indicated 
tonnage  is,  of  course,  doubled  so  that  the  tensile  strength  is 
reported  in  terms  of  tons  per  square  inch. 

In  works  practice  a  gauge  is  used  to  see  if  the  turned  test- 
pieces  are  of  the  correct  diameter.  Special  scales,  slide  rules, 
and  tables  are  also  used  to  facilitate  calculations,  for  all  test- 
pieces  are  not  cut  or  turned  to  set  sizes.  But  as  a  student 

*  Tensile  strength  means  the  strength  or  power  to  hold  together 
while  subjected  to  a  force  tending  to  stretch  or  sunder  by  pulling. 


144  IRON   AND   STEEL   MANUFACTURE. 

should  be  able  to  calculate  areas,  &c.,  without  such  aids  the 
following  explanations  and  examples  may  prove  useful.  The 
decimal  system  is  in  use  in  test  houses.  The  cross  area  of  a 
flat  test-piece  is  ascertained  by  measuring  the  breadth  and 
the  thickness,  converting  any  vulgar  fractions  into  decimal 
equivalents,  and  multiplying  one  dimension  by  the  other. 

To  Ascertain  the  Cross  Area  of  a  Cylindrical  Piece. — Square 
the  diameter  and  multiply  the  result  by  '7854- 

Example. — What  is  the  cross  area  of  a  test-piece  which  has 
been  turned  to  '797  inch  diameter? 

•797  X  '797  x  '7854  =  -635209  x  '7854 

•635209  x  '7854  =  '49889 
and  -49889  =  cross  area. 

To  Compute  the  Tensile  Strength  of  a  Test-piece. — Divide 

the  indicated  tonnage  by  Us  original  cross  area. 

Example. — A  test-piece   *8  inch   diameter  broke  under  a 
maximum  stress  of  1 6  '8  tons.    What  was  its  tensile  strength  1 
•8  X  '8  X  '7854  =  -50265, 

16'8      -33-42 
^50262-         l2' 

and  33-42  =  tensile  strength  per  square  inch. 

To  Compute  the  Percentage  Elongation  of  a  Test-piece. — 

Find  the  difference  in  the  distance  between  the  punch  marks  on  the 
piece  before  and  after  rupture.  Divide  the  difference  by  the  original 
distance,  and,  in  order  to  find  the  percentage  elongation,  multiply 
the  result  by  100. 

Example. — Distance  between  the  marks  when 

the  test-piece  broke  =  9 '82  inches. 

Distance  between  the  marks  on  the  test- 
piece  before  fixing  it  in  the  testing 
machine  =  8'00 


Difference   =  1'82      „ 

Then,      "»  x  100  =  32.75 

o 

and  22-75  =  elongation  per  cent. 


MECHANICAL    TESTING    OF    STEEL    AND    IRON.  145 

To  Compute  the  Percentage  Contraction  of  Area  of  a  Test- 
piece. — Find  the  difference  between  its  cross  area  before  and  after 
testing.  Divide  that  difference  by  the  original  cross  area,  and,  in 
order  to  find  percentage,  multiply  the  result  by  100. 

Example. — Diameter  of  the  piece  before  testing  =  '800  inch. 
Diameter  of  the  test-piece  when  broken  =  '521  „ 

Then,  '8  x  '8  x  '7854  =  -50265  inch. 

•521   X  -521   x  '7854  =  '21319 


Difference  =  '28946     „ 

'28946  x  100 

•50265 
5  7 '5  8  =  percentage  contraction  of  area. 

The  quality  of  a  certain  make  of  steel  will  depend  chiefly 
on  (a)  its  composition,  (J)  the  working  of  the  steel  in  the 
furnace  or  converter,  and  (c)  the  treatment  to  which  it  was 
subjected  after  being  poured  into  the  ladle. 

The  percentage  of  carbon  will,  to  a  large  extent,  influence 
its  tensile  strength  and  its  elongation.  Within  limits,  the 
higher  the  percentage  of  carbon  present  the  greater  will  be  its 
tensile  strength  and  the  less  its  capacity  for  elongation  before 
breaking.  The  other  elements  present  will  have  a  marked 
effect  on  its  mechanical  properties.  Malleable  metals  are 
improved  by  judicious  manipulation,  such  as  rolling  at  proper 
temperature. 

Mild  steels  generally  have  composition  near  to  the 
following : — 

Carbon, '17* 

Phosphorus, '05 

Sulphur, -05 

Silicon, -02 

Manganese.         ......  '50 

Iron  (by  difference), A 

100-00 

*  The  percentage  of  carbon  is  purposely  varied  to  suit  the  purpose 
for  which  the  steel  is  intended. 

10 


146 


IRON    AND    STEEL    MANUFACTURE. 


The  tensile  strength  of  such  steel  is  generally  equal  to  from 
27  to  32  tons  per  square  inch,  with  an  elongation  of  from  16 
to  22  per  cent,  on  8  inches. 

SPECIFICATIONS  FOE  MILD  STBKL. 


Tensile 
Strength  in 
Tons  per 
Square  Inch. 

Percentage  Elongation 

Ship  plates- 
Admiralty,       .        .        ~.  '  r 
Lloyds,     .        ...       V 

26  to  30 

28  „  32 

20  per  cent,  on  8  ins. 
16      ,,         ,,         „ 

Boiler  plates  — 
Admiralty,       .        . 
Board  of  Trade, 
Lloyds,    .... 

27    ,  30 
27    ,  32 
27    ,  32 

20      , 

18      , 
20      , 

Boilers  (other  parts)  — 
Admiralty,       .        .  '  '.'t  .. 
Board  of  Trade,        .     :  r  > 
Lloyds,    .        .        .  V   «  '' 

24    ,  27 
26    ,  30 
26    ,  30 

25      , 
20      , 
20      , 

Steel  for  bridge  building,    . 

27  „  31 

20  per  cent,  on  8  or  10  ins. 

Pieces  which  have  been  rolled  into  thin  sections  or  drawn 
into  wire  yield  better  results  than  thicker  sections. 

Common  wrought  iron  may  contain — 

Carbon,  W  C-/  ',!  ''  X  '  .  '  v\'"  . ..  '05 
Phosphorus,  \-  .^'^»'  .  V  •/  "35 
Sulphur,  v  ,-  v^;>V»  ;"  •  ?  •  V  .  *06 

Silicon,  '...•.'•.;'->,'  '•.vi-v\-v;<-;.?v',  .V.'':  '23 
Slag,.  ;V^*  i^  ;,.^\wv  ',  .;  .  about  3 '3 

Best  wrought  iron  may  contain — 


Carbon,      .        -.'        .'  "V 

•:  -TV  '.'-•*••••'.••-%      '06 

V"'  •••;-:-''-ik  .'      .       *04 

Silicon, 

k  '/    ••  "  ""»••'  •'•'•••.         '20 

:.'  ••V-V''^6V;    "  '.            '06 

Slag. 

,    about  2*8 

MECHANICAL  TESTING  OP  STEEL  AND  IRON. 
STRENGTH  OF  WROUGHT  IRON. 


147 


Tensile 

Strength 
in  Tons  per 
Square  Inch. 

Percentage 
Elongation. 

Percentage 
Contraction. 

Puddled  bar,  . 

18-6 

4  to    8 

4-5 

Common  iron, 

21-0 

8  „  16 

5-3 

Treble  best,     . 

23-0 

12  ,,25 

15  to  35 

STRENGTH  OF  CAST  IRON. 

For  testing  the  power  of  iron  castings  to  withstand  crushing, 
test-pieces  3  inches  by  1  inch  are  prepared,  and  they  show  a 
resisting  power  of  25  to  90  tons,  with  a  probable  average  of 
about  45  tons. 

For  testing  the  transverse  strength  of  castings,  a  bar  2  inches 
deep  by  1  inch  in  breadth  is  laid  on  supports  3  feet  apart. 
Under  these  conditions  common  iron  will  carry  from  23  to  27 
cwts.,  and  better  iron  will  carry  from  28  to  31  cwts.,  with  a 
deflection  of  *3  inch. 


148 


CHAPTER     XV. 
FOUNDRY  PRACTICE— IRON  AND  STEEL  CASTINGS. 

THE  object  of  the  iron-founder  is  fo  "  cast "  or  form  pig  iron 
into  shapes  required.  This  he  does  by  pouring  melted  pig 
iron  into  prepared  moulds,  so  that  the  "  castings "  will  be  of 
the  desired  size,  shape,  and  strength. 

For  the  production  of  sound  and  shapely  castings  the 
melted  "  metal "  must  be  of  suitable  chemical  composition, 
and  must  be  cast  at  proper  temperature  in  reliable  moulds 
Increasing  attention  is  now  being  paid  to  these  points. 

The  moulds  must  be  of  material  which  will  withstand, 
without  softening  or  fusing,  the  heat  of  the  molten  pig  iron; 
the  material  must  have  coherency — that  quality  which  binds 
it  together  so  as  to  hold  against  the  pressure  of  the  fluid  metal 
— it  must  be  close  enough  to  contain  the  liquid  metal,  while, 
at  the  same  time,  open,  or  porous  enough  to  permit  the  escape 
of  gases  which  are  liberated  from  the  melted  metal  during 
solidification.  The  chief  constituent  of  the  material  for  the 
mould  is  silica  *  (Si02),  as  shown  in  the  following  analyses  : — 


Constituents. 

Chemical 
Formulae. 

Fire 
Sand. 

Moulding 
Sand. 

Core 
Sand. 

Silica,  . 

Si02 

98-0 

86-0 

94-3 

Alumina, 

A^Oo 

1-5 

8-5 

2-0 

Iron  oxide, 

FeoOo 

o-i 

2-0 

0-3 

Lime,  .           "     . 

CaO 

0-2 

0-5 

o-o 

Carbonate  of  lime, 

CaC03 

0-3 

1-6 

Magnesia, 
Alkalies, 

MgO 
Na20  and  K2O 

b-i 

0-8 

o-i 

0-5 

o-i 

Combined  water, 

H20 

o-i 

1-5 

1-0 

Organic  matter,  . 

... 

0-3 

0-2 

100-0 

100-0 

100-0 

*  White  sand  is  a  familiar  example  of  silica  ;  a  still  better  example  of 
pure  silica  is  quartz,  a  hard,  glistening  substance. 


IRON    AND   STEEL   CASTINGS.  149 

Fire  sand  is  useful  for  mixing  so  as  to  increase  the  power 
of  withstanding  a  very  high  temperature,  and  especially  for 
steel-casting  purposes.  It  is  also  useful  for  correcting  a 
moulding  sand  which  is  too  apt  to  bind. 

Moulding  sand  of  the  composition  stated  is  suitable  for 
medium  iron  work.  For  lighter  iron  work  moulding  material 
with  82  per  cent,  of  silica  is  suitable ;  for  heavy  iron  work  the 
silica  may  amount  to  88  per  cent.,  or  over. 

In  moulding  materials  silica  is  the  fire-resisting  substance. 
Alumina  is  also  refractory,  but  it  "bakes  together"  when  heated 
with  silica — it  possesses  "bond."  When  too  much  alumina 
is  present  there  is  danger  of  the  mould  being  spoiled  by 
excessive  shrinkage  or  by  being  non-porous.  A  sand  low  in 
alumina  and  iron  will  permit  of  the  rapid  escape  of  gases ; 
with  high  alumina  the  sand  bakes  and  holds  back  the  gases. 
"  Organic  matter  gives  bond  to  sand,  but  the  bond  or  binding 
property  is  destroyed  the  moment  it  comes  in  contact  with  the 
molten  metal,  the  organic  matter  being  burned  out;  conse- 
quently there  is  a  loss  in  volume,  and  this  shrinkage  causes 
the  sand  to  fall  or  crumble."  *  The  other  ingredients  men- 
tioned in  the  table  tend  to  cause  the  material  to  fuse  or  melt. 
Alkalies  (potash  and  soda)  are  specially  bad.  Being  thus 
objectionable  they  can  only  be  tolerated  in  small  amount. 

The  mechanical  condition,  the  intimacy  of  intermixture,  the 
pressure  to  which  the  substance  has  been  subjected  while 
in  its  native  bed,  and  the  fineness  to  which  the  particles  have 
been  ground — all  these  have  an  important  bearing  on  the 
quality  of  moulding  material.  The  proof  of  its  fitness  or  un- 
fitness  may  best  be  found  by  trial.  But  chemical  analysis 
may,  in  a  most  helpful  degree,  suggest  the  proper  proportion  in 
which  to  mix  with  some  other  material  to  produce  a  good 
moulding  compound. 

The  moulding  material  must  be  of  the  proper  grain;  its 
binding  power  may  be  increased  by  admixture  with  clay,  or 
with  tar,  or  with  cheap  gum.  Cores  have  been  made  of  pure 
sand  and  thick  oil.  Porosity  may  be  improved  by  judicious 

*  C.  Scott,  see  paper  by  J.  E.  Stead,  F.R.S.,  Cleveland  Institute  of 
Engineers,  Feb.  1905. 


150  IRON    AND   STEEL    MANUFACTURE. 

admixture  with  coal  dust.  Binding  power  is  sometimes  im- 
proved at  the  expense  of  porosity ;  improved  porosity  may 
mean  corresponding  diminution  in  binding  power.  Chopped 
straw,  cow  hair,  horse  dung,  &c.,  are  mixed  with  sand  and 
loam.  They  give  additional  strength,  and,  as  they  burn  off, 
leave  passages  for  the  escape  of  gases. 

Green-sand  is  the  term  applied  to  moulds  made  of  sand 
in  its  natural,  raw,  'or  green  state.  The  composition  of  the 
sand  may  be  correct  for  light  castings,  or  an  addition  of  5 
or  6  per  cent,  of  fireclay  may  be  necessary  for  heavy  castings. 
Green-sand  moulds  need  a  facing,  about  an  inch  in  thickness,  of 
a  mixture  of  sand  and  coal  dust  towards  the  hot  metal.  The 
coal  dust  prevents  fusion,  and  the  castings  have  a  cleaner 
surface.  The  surface  is  blacked  with  graphite  (plumbago),  or 
other  suitable  substances.  For  dry-sand  castings  the  moulds 
are  carefully  dried  before  pouring  in  the  metal.  This  takes 
time,  and  increases  the  cost.  For  large  castings  loam  moulds 
are  prepared.  ,Loam  moulding  is  the  most  expensive  form  of 
founding,  but  is  practically  the  only  one  for  certain  purposes. 

The  Melting  of  "  Metal "  for  Foundry  Purposes. — In  a  few 
works  the  "  metal,"  as  it  comes  from  the  blast  furnace,  is  run 
directly  into  ironfounders'  moulds.  But,  as  a  rule,  it  is  cast 
into  "  pigs  "  (see  p.  208),  which  are  allowed  to  solidify,  and 
are  afterwards  graded  and  remelted  in  the  foundry.  Metal 
for  special  purposes  is  remelted  in  reverberatory  furnaces,  as 
they  are  well  under  control  and  can  discharge  at  one  time 
a  large  quantity  of  fluid  metal  of  uniform  composition. 
When  melted  metal  is  required  in  small  quantities  only,  the 
pig  iron  is  remelted  in  crucibles.  For  general  foundry  pur- 
poses a  cupola  is  employed  for  remelting.  A  Bessemer  works' 
cupola  has  been  described  on  p.  71,  and  it  differs  from  the 
foundry  cupola  chiefly  in  size.  A  Bessemer  cupola  is  worked 
day  and  night ;  as  a  rule,  a  foundry  cupola  is  not. 

Foundry  Cupolas. — A  foundry  cupola  is  an  upright  cylin- 
drical structure  of  firebrick  encased  in  rivetted  boiler  plates. 
Internal  rings  or  angle  irons  are  attached  at  intervals  -  to  the 
plates  for  supporting  the  brickwork.  An  air  blast  is  injected 
through  tuyeres,  which  may  be  in  one  row  or  more.  For 


IRON    AND   STEEL   CASTINGS. 


151 


Fig.  61.— Foundry  Cupola  with  Solid  Bottom. 


152 


IRON  AND   STEEL   MANUFACTURE. 


Fig.  62.— Foundry  Cupola  with  Drop  Bottom, 


IRON    AND   STEEL    CASTINGS. 


153 


heavy  foundry  work  the  tuyeres  are  placed  higher  than  for 

small  foundry  work.     Pig  iron,  fuel,  and  flux  are  charged  into 

the  hot  cupola ;  molten  metal  is  tapped  out,  when  required, 

and  runs   from   the   taphole   along  a 

spout  or  launder  into  the  casting  ladle. 

For  small  foundry  work  the  spout  is 

placed    about    20    inches    from    the 

ground ;  for  heavier  work  it  is  placed 

higher.     From  larger  cupolas  slag  is 

tapped    off  from    the   slaghole    as    it 

gathers. 

Some  cupolas  have  solid  bottoms,  as 
shown  in  fig.  6 1 ;  others  are  con- 
structed with  a  "  drop "  iron  bottom 
plate,  as  shown  in  figs.  62  and  63. 

On  an  iron  foundation  plate  four 
massive  cast-iron  columns  are  set; 
these  support  a  substantial  base  plate 
which  carries  the  shell  of  the  cupola. 
When  the  bottom  plate  is  removed, 
or  unfastened,  the  materials  left  in 
the  cupola — those  which  have  not  been 
tapped  out — are  -removed.  Fig.  63 
shows  a  section  of  such  a  "drop- 
bottom"  cupola  erected  to  the  specifi- 
cation of  Mr.  Robert  Buchanan  in 
the  Soho  Foundry  of  Messrs.  W.  &  T. 
4very,  Limited.  Its  tuyeres  are  not 
at  one  uniform  level,  but  are  arranged 
as  points  in  a  spiral.  Beneath  the 
lowest  tuyere,  in  the  tuyere  belt,  is  a 
ping  composed  of  an  alloy  which  melts 
very  readily,  and  in  the  event  of  slag 
or  metal  rising  accidentally  to  an  in- 
convenient extent,  the  "  fusible  plug  " 
melts,  and  thus  an  outlet  is  provided 
and  damage  to  the  tuyere  is  prevented. 

Fig.  64  shows  a  view  of  one  of  the  improved  rapid  cupolas 
erected   by   Messrs.   Thwaites   Brothers,  Bradford.     An  im- 


/ 

"*"'"*-  ; 

'f, 

y 

y 

6  E 

I 

y 

/ 

t 

f^-^ 

|             j 

o 

^ 

/     O       % 

j 

0.  £-^ 

i    °% 

^                ^ 

c  — 

IT1 

A=^^    - 

-IfJ  1 

—  A 

Fig.  63. — Section  of 
Koundry  Cupola 
with  Drop  Bottom. 

A,  Columns. 

C,  Drop  bottom. 

D,  Tuyere. 

E,  Air  belt. 

F,  Iron  angle. 

G,  Charging  platform. 
H,  Charging  door. 

I,    Iron  shell. 
J,    Brickwork. 


154 


IBON   AND    STEEL   MANUFACTURE. 


portant  adjunct  is  the  receiver,  which  is  lined  with  firebrick, 
and  connected  with  the  cupola  by  a  brick-lined  channel.  It 
has  usually  about  half  the  hourly  melting  capacity  of  the 
cupola.  The  hot-air  pipe  between  the  receiver  and  the  cupola 
supplies  sufficient  hot  air  from  the  latter  to  prevent  the 
chilling  of  the  "  metal." 


Fig.  64. — Foundry  Cupola  with  Drop  Bottom  and  Receiver. 

The   blast   required   for  a  cupola  is  usually  supplied  at 
a  pressure  of  about  1 0  ozs.  per  square  inch.*  "  The  quantity  of 
air  needed  is  about  650  cubic  feet  per  minute  for  each  ton  of 
*  Equal  to  a  21 -inch  column  on  a  water  gauge. 


IRON    AND   STEEL   CASTINGS. 


155 


pig  iron  melted.  The  amount  and  pressure  vary  according 
to  circumstances.  An  economical  and  convenient  appliance 
for  supplying  the  required  air  blast  is  the  Boots  blower, 


Fig.  65. — Roots'  Blower  with  Electric  Motor. 

which  is  illustrated  in  figs.  65  and  6G.     As  made  by  Messrs. 
Thvvaites  Brothers,  Bradford,  Yorks,  the  blower  consists  of 


Fig.  66. — Section  of  Roots'  Blower. 

a  carefully-machined  cast-iron  case  which  is  elliptical  in  cross 
section.  The  end  plates  are  bored  by  a  duplex  machine  for 
the  journals  of  the  shafts  for  the  revolvers.  Each  revolver  is 


156  IRON   AND    STBEL    MANUFACTURE. 

cast  in  one  piece,  accurately  machined  all  over  to  gauge, 
specially  centred,  and  carefully  balanced.  Conical  adjustable 
bearings  are  used.  Geared  wheels  are  introduced  to  equalise 
the  power  transmitted  to  the  revolvers.  Oil  baths  set  for  the 
lower  part  of  each  wheel  ensure  comparatively  silent  and 
smooth  working.  Generally  there  is  a  wooden  cover  with 
perforated  metal  panels  on  the  top  of  the  cylinder,  but 
sometimes  the  air  inlet  is  placed  on  one  side. 

The  blower  is  mounted  on  a  bed  plate,  and  may  be  driven 
by  TDelt,  by  steam  engine  direct,  or  by  a  motor.  For  a  cupola 
melting  about  4  tons  of  pig  iron  per  hour  the  blower  may  be 
worked  at  380  revolutipns  per  minute;  for  cupolas  of  greater 
capacity  the  revolutions  will  be  less,  but  the  driving  pulleys 
will  be  of  greater  diameter. 

Fans  are  frequently  used  for  forcing  the  air  required  for 
cupolas. 

Working  a  Foundry  Cupola. — When  the  cupola  has  been 
brought  into  working  condition  a  coal  fire  is  kindled  and  then 
covered  with  a  "  bed  "  of  coke.  When  the  coke  has  burned 
up  to  the  level  of  the  tuyeres,  the  door  near  the  bottom  of 
the  cupola,  as  described  in  p.  71,  is  placed  in  position,  and 
charging  from  the  charging  door  is  begun. 

Mr.  Robert  Buchanan  gives  the  following  particulars*: — 

Bed  of  coke  =  5  cwts. 

Five   charges   of    10    cwts.   of  pig  iron,  alternating  with 

1  i  cwts.  of  coke. 
Alternate  charges   of   10  cwts.  of  pig  iron  with   1   cwt. 

of  coke. 
Towards  the  end  of  the  working  day  the  proportion  of  coke 

is  further  diminished. 

The  amount  of  coke  consumed  varies,  1  Ib.  of  coke  sufficing, 
on  an  average,  to  melt  10  Ibs.  of  "metal"  for  heavy  castings, 
or  8  Ibs.  of  "  metal "  for  light  castings. 

Limestone  is  also  charged  into  the  cupola  to  supply  lime  to 

combine  with  the  ash  of  the  coke  and  the  sand  on  the  pig  iron 

to  form  a  fusible  slag.     The  amount  of  limestone  used  varies 

between  a  quarter  and  a  half  hundredweight  per  ton  of  metal. 

*  Proceedings  of  the  Sta/ordahire  Iron  and  Steel  Institute,  Nov.  1901. 


IRON    AND   STEEL   CASTINGS. 


157 


Foundry  Ladles  are  of  cast  iron  if  small,  of  wrought  iron  or 
mild  steel  if  larger,  and  have  a  capacity. of  from  half  a  hundred- 


* 


so 


weight  up  to  several  tons.     They  are  lined   with  refractory 
materials  and  should  be  heated  before  using.     Figs.  67  and 


158 


IRON    AND    STEEL   MANUFACTURE. 


68  represent  hand  ladles  used  for  small  castings.     In  Fig.  69 
is  shown  a  large-sized  geared  crane  ladle,  as  manufactured  by 


to 

£ 


Messrs.  Thwaites  Brothers,  Bradford.     A  trolley  ladle,  which 
is  convenient  for  conveying  and  dealing  with  foundry  metal, 


IRON   AND   STEEL  CASTINGS 


159 


160  IRON    AND    STEEL    MANUFACTURE. 

is  illustrated  in  Fig.  70.     The  latter,  made  by  C.  M'Neil, 
Glasgow,  is  of  stamped  steel,  without  weld  or  rivets. 

The  contents  of  the  ladles  are  generally  emptied  over  a 
lip  or  spout,  the  ladle  being  tilted  as  required  and  the  slag 
held  back  during  pouring  when  necessary. 

Pig  Iron  for  Foundry  Use. — The  pig  iron,  or  mixture  of  pig 
irons,  should  be  of  a  composition  suited  to  the  qualities  needed 
in  the  castings  which  are  to  be  produced.  A  strong,  heavy 
casting  is  best  made  from  pig  iron  which  is  not  suited  for 
light  ornamental  work,  and  "  metal "  which  is  well  adapted 
for  light  work  does  not  suit  for  strong  castings.  It  is  a 
costly  mistake  to  attempt  to  improve  certain  castings  by 
incorporating  high-priced  hematite  pig  iron.  The  author 
has  frequently,  with  most  satisfactory  results,  advised  the 
introduction  of  more  cheap  pig  iron  in  mixtures.  There 
is  in  the  minds  of  many  foundrymen  a  notion  that  in  order 
to  make  good  castings  costly  pig  iron  is  necessary,  and  when- 
ever trouble  comes  and  castings  are  faulty,  tests  bad,  and 
rejections  numerous,  recourse  is  had  to  hematite  as  the  cure 
for  all  ills.  '  It  is  equally  a  mistake — although  not  by  any 
means  so  common — to  seek  to  improve  all  mixtures  by  using 
cheap,  highly-phosphoric  pig  irons.  The  purchase  and  use 
of  a  first-class  foundry  pig  iron,  of  a  good  old  standard 
brand,  is  often  a  profitable  investment  for  the  foundryman. 
Castings  which  have  been  proved  by  long  and  useful  service 
to  be  excellent  do  not  vary  in  composition  to  any  great 
extent. 

By  selecting  grey  and  white,  or  grey  and  mottled  pig,  irons 
in  such  proportions  that  the  chemical  composition  will  yield 
"metal"  from  the  cupola  of  the  composition  required,  one 
of  the  first  conditions  for  the  production  of  suitable  castings 
will  be  complied  with.  The  changes  in  composition  which 
pig  iron  undergoes  while  passing  through  the  cupola — such 
as  oxidation  of  iron,  diminution  in  percentage  of  silicon  and  of 
manganese,  increase  in  percentage  of  sulphur,  and  the  slight 
increase  in  percentage  of  phosphorus — must,  of  course,  be 
allowed  for  in  making  up  the  cupola  charge.  With  well- 
arranged  and  well -finished  moulds  of  proper  materials, 
suitable  metal,  attention  to  the  best  temperature  at  which 


IRON    AND    STEEL    CASTINGS.  161 

to  pour,  and  the  rate  at  which  the  castings  are  allowed  to 
cool,  waste  will  be  reduced  to  a  minimum. 

Silicon  is  the  element  in  pig  iron  which  has  a  dominant 
effect,  either  directly  or  indirectly,  in  modifying  the  character 
of  a  casting.  It  has  a  marked  effect  on  the  condition  of 
the  carbon.  When  the  percentage  of  silicon  is  high  the 
carbon  is  mostly  in  the  graphitic  state,*  and  the  sulphur 
is,  as  a  rule,  low.  Such  a  pig  iron  is  grey,  unless  produced 
under  abnormal  blast-furnace  conditions.  A  pig  iron,  or 
a  mixture  of  pig  irons,  containing  a  fair  proportion  of  silicon, 
is  well  adapted  for  casting,  because  it  is  very  fluid  when 
melted,  fills  the  mould  well,  and  makes  a  casting  which  is 
likely  to  be  free  from  blowholes.  A  soft  grey  pig  iron  is 
best  suited  for  castings  which  are  to  be  tooled. 

Professor  Turner  investigated  the  relations  between  chemical 
composition  and  mechanical  qualities,  and  found  that — 

Castings  of  maximum  tensile  strength  contained  1  '8  per  cent,  of  silicon. 
,,  ,,         transverse    ,,  ,,         I '4        ,,  ,, 

,,  „        crushing       „  „        0'75      „ 

Phosphorus  in  pig  iron  increases  the  fluidity  but  reduces 
the  strength.  Sulphur  tends  to  whiten  the  iron  and  may,  to 
a  limited  extent,  add  to  its  strength.  Its  presence  beyond  a 
limited  amount  is  objectionable.  In  experiments  conducted 
by  Mr.  Chas.  Wood,  the  presence  of  0*16  per  cent,  of  sulphur 
did  not  appear  to  be  harmful. 

The  effects  of  carbon  in  castings  are  most  marked.  "  Com- 
bined carbon  is  mainly  the  determining  factor  of  the  hardness 
and  shrinkage  of  a  casting.  .  .  .  For  general  engineering 
foundry  castings  about  0'5  per  cent,  is  a  fair  amount.  .  .  . 
The  total  carbon  should  not  exceed  3 '2 5  per  cent,  either  in 
hard  or  soft  castings."f  When  pig  iron  contains  a  high  per- 
centage of  graphitic  carbon  the  plates  of  graphite  are  generally 
large,  and,  as  they  distinctly  break  the  metallic  continuity  of 
the  casting,  its  strength  is  lessened.  Professor  Turner  has 
investigated  the  influence  of  size  of  graphite  plates  in  castings 
with  important  results. 

*See  p.  12. 

tJ.    E.    Stead,    paper   read    before   the   Cleveland    Institution   of 
Engineers,  February,  1905. 


162  IRON   AND   STEEL   MANUFACTURE. 

APPROXIMATE  ANALYSIS  OF  OBEY  FOUNDRY  PIG  IRON. 


Chemical 
Symbols. 

~~l 

Per  cent. 

Graphitic  carbon,                 ,         v        »         • 

C 

c 

3-25 
0-25 

c 

3-50 

Silicon,         ...                          •        • 

Si 
P 

2-50 
0-80 

s 

O'lO 

Mn 

1-30 

Fe 

A 

100-00 

COMPOSITION  OF  IRON  CASTINGS. 


Chemical 
Symbols. 

Heavy, 
Strong. 

Light, 
but  Fairly 
Strong. 

Ornamental. 

Carbon,    . 
Silicon,     . 
Phosphorus, 
Sulphur,  . 
Manganese, 
Iron, 

C 

Si 
P 
S 
Mn 
Fe 

3-5 
1-9 

06 
0-09 
0-5 
A 

3-8 
2-3 
0-8 
0-08 
0-5 
A 

4-0 
2-8 
1-0 
0-09 
0-5 
A 

100-00 

100-00 

100-00 

Cast  iron  can  be  softened  by  altering  its  composition, 
especially  by  enriching  with  silicon,  or  by  allowing  to  cool 
slowly.  And  it  can  be  hardened  by  remelting,  so  as  to 
eliminate  silicon,  or  by  causing  it  to  cool  quickly — as  in  the 
making  of  chilled  castings.  Materials  which  are  known  in 
foundry  practice  as  softeners  are  regularly  produced,  and  they 
are  useful  in  "  correcting  "  irons  which  are  too  hard,  and  for 
promoting  soundness  in  castings.  Softeners  must,  of  course, 
be  added  "  with  brains." 

For  composition  of  softeners  see  p.  238. 


When  melted  grey  pig  iron  is  allowed  to  stand  for  some 
time  in  a  ladle?  kish?  which  consists  largely  of  graphite  and 


IRON   AND   STEEL   CASTINGS.  163 

contains  notable  amounts  of  manganese  and  sulphur  (all  of 
which  are  eliminated  from  the  iron),  collects  on  the  surface. 

A  ladleful  of  melted  pig  iron,  especially  if  covered  with 
ground  coke,  or  any  other  suitable  substance  which  will 
retard  cooling,  will  remain  in  teeming  condition  for  a  long 
time. 

Remelting  of  pig  iron  is,  and  repeated  remeltings  may  be,  up 
to  a  certain  point,  beneficial.  But  as  some  silicon  is  eliminated 
during  each  remelting,  it  is  clear  that  when  the  silicon  has 
reached  the  proper  percentage  for  the  purpose  in  view  any 
further  remelting  must  be  a  dis- 
tinct disadvantage.  Manganese 
is  also  lessened  in  amount  during 
each  remelting,  and  sulphur  (un- 
less precautions  are  taken)  is 
increased. 

Chilled     Castings.  —  Certain 
castings  have  parts  of  their  sur- 
faces    purposely    hardened    by 
being  cast  in  moulds  which  are     Fig.  71.— Chilled  Casting, 
partly  of  iron.      Thus   a  wheel  S  =  Sand  mould, 

may  be  hardened  on  the  wearing  =  ^°4T!    " 

surface  of  the  rim,  and  the  centre 

of  the  nave  may  be  also  hardened.  Fig.  71  may  convey  an 
idea  of  how  the  superficial  hardening  is  induced.  The  chill 
is  not  deep,  and  the  comparative  pliancy  and  absence  of 
brittleness  of  the  portions  which  have  not  been  chilled  are 
advantageous. 

The  crystallisation  of  cast  iron  calls  for  consideration. 
Iron,  like  other  metals,  crystallises  at  right  angles  to  the  surface 
which  is  cooled.*  If  a  casting  is  not  designed  with  a  due 
regard  to  the  formation  of  crystals  its  strength  may  be 
insufficient.  The  earlier  cylinders  employed  at  the  erection 
of  the  Menai  Bridge  had  sharp  corners,  as  shown  in  fig.  72, 
and  they  soon  broke  along  the  lines  of  weakness,  as  represented 

*  A  piece  of  common  spelter  (ingot  zinc)  shows  well  the  lines  of 
crystallisation  in  cast  metal 


164 


IRON    AND  -STEEL    MANUFACTURE. 


in  fig.  73.  The  form  sketched  in  fig.  74  was  an  improved 
design,  which,  having  no  pronounced  lines  of  weakness,  with- 
stood the  heavy  pressure.  The  lines  of  crystallisation  in  a 


Fig.  72. — Section  of  Original  Fig.  73.  —Section  of  Cast -iron 

Cast-iron  Cylinder — Sketch  Cylinder     (broken)  —  Sketch 

Showing     Arrangement     of  Showing      Arrangement      of 

Crystals.  Crystals. 

circular  casting  are  shown  in  fig.  75,  and  figs.  76   and    77 
indicate  the  crystallisation  in  a  square  and  a  long  iron  casting. 


Fig.   74. — Improved  Section  of  Cast-iron  Cylinder — Sketch 
Showing  Arrangement  of  Crystals. 


Fig.  76. — Circular  Casting. 


Fig.  76. — Square  Casting. 


IRON  AND  STEEL  CASTINGS.  165 

In  making  castings,  the  shrinkage  which  occurs  must  be 
allowed  for;  they  must  be  cast  larger  than  the  finished  pro- 
ducts are  required  to  be.  The  amount  of  shrinkage  varies 
with  the  class  of  pig  iron,  and  also  with  the  size  of  the  casting. 


Fig.  77.  —  Long  Casting. 

Massive  castings  do  not  shrink,  relatively,  as  much  as  lighter 
ones  do.     As  a  general  indication  of  the  trade  practice  the 
following  figures  are  useful  :  — 
The  allowance  for 

Massive  castings  is    .         .    i  inch  in  18  inches. 
Medium        .,  .         .    £      „         15       „ 

.         .  12 


STEEL  CASTINGS. 

The  chief  difficulties  in  the  way  of  producing  good  steel 
castings  arise  from  the  high  temperature  at  which  it  is 
necessary  to  produce  and  teem  the  metal,  the  unsatisfactory 
nature  of  iron-moulding  material  for  steel  castings,  the  great 
skrinkage,  and  the  want  of  soundness  and  strength  in  the 
finished  material,  due  in  large  measure  to  the  great  quantity 
oi  gas  which  steel  is  apt  to  occlude.  By  occluding  is  meant 
that  power  by  which  melted  metals  can  dissolve  many  times 
their  own  bulk  of  gases  and  retain  them  fw  a  time.  Some  of 
the  occluded  gases  become  liberated  during  the  cooling  of 
the  metal,  and,  after  a  crust  has  formed,  they  cannot  easily 
escape.  In  these  circumstances  gases  gather  in  one  or  more 
parts  of  the  casting  and  form  cavities  or  blowholes. 

The  temperature  at  which  the  "metal"  for  steel  castings 
melts  is  said  to  be  from  1,450°  C.  (=  2,642°  F.)  to  1,500°  C. 
(=  2,732  F.),*  and  a  higher  temperature  must  be  employed. 

*The  temperatures  expressed  here  were  ascertained  by  a  modem 
pyrometer  which  indicates  much  lower  (but  probably  more  accurate) 
degrees  for  high  temperature.  The  older  heat  measurements  of  high 
temperatures  are  not  reliable. 


166 


IRON    AND   STEEL    MANUFACTURE. 


A  satisfactory  moulding  material,  capable  of  withstanding  the 
great  heat,  and  yet  porous  enough  to  allow  free  escape  of  the 
large  volume  of  contained  gases,  is  made  by  heating  quartz, 
quenching  in  water,  grinding  to  powder,  and  mixing  with 
clay  in  proper  proportion.  The  prepared  moulds  require  to 
be  well  faced  with  graphite.  The  shrinkage  is  about  double 
that  of  iron  castings.  It  is  usual  to  strip  the  castings  as  soon 
as  permissible,  the  cores,  &c.,  being  removed  early. 

The  troubles  incidental  to  the  introduction  of  a  new  branch 
of  manufacture  have  been  overcome,  and  sound  steel  castings 
are  now  made  with  fair  regularity.  Steel  for  castings  is 
produced  in  crucibles,  in  converters,  and  in  open -hearth 
furnaces.  As  it  is  not  easy  to  keep  the  metal  hot  during 
the  long  time  occupied  in  casting  large  quantities,  small 
furnaces  and  converters  are  in  general  use  for  steel  founding. 
Basic  steel  castings  are  in  some  instances  preferred  to  those  of 
acid  steel.  The  procedure  for  producing  steel  for  castings  in 
open-hearth  furnaces  is  much  the  same  as  for  the  production 
of  ingots.  For  castings  it  is  essential  that  the  steel  should 
be  finished  hot,  and  in  practice  ferro-silicon  (see  p.  238)  is 
freely  but  judiciously  used. 

Steel  castings  vary  widely  in  chemical  composition,  each 
tap  of  metal  being  finished  to  suit  the  order  in  hand.  The 
following  are  examples  : — 


Percentage  of 

Carbon. 

Silicon. 

Phos- 
phorus. 

Sulphur. 

Man- 
ganese. 

Stern  frame,    . 

•17 

•50 

•055 

•048 

•56 

Railway  wheel, 
Railway  wheel, 

•30 
•44 

•27 
•38 

•065 
•051 

039 
•043 

•63 

•51 

Crank  axle, 

•34 

•15 

•041 

•042 

•56 

Bracket,  . 

•41 

•57 

•060 

•068 

66 

167 

CHAPTER   XVI. 
MALLEABLE    CASTINGS. 

NUMEROUS  small  articles  of  intricate  shape,  and  fairly  strong, 
are  in  daily  demand — such  articles  as  keys,  parts  of  locks, 
nozzles,  hooks,  &c.  It  would  not  pay  to  fashion  keys  by 
hammering  wrought  iron  into  shape,  and  cast-iron  keys  would 
not  be  strong  enough,  unless  heavy.  Hence  the  desire  for  a 
process  by  which  some  of  the  qualities  of  wrought  iron  may  be 
conferred  on  castings  of  complicated  shape.  The  castings  can 
be  more  cheaply  worked  out  by  a  sand  pattern  than  in  the 
iron  itself.  By  the  annealing  process  to  which  they  are  sub- 
jected, important  changes  are  effected  by  which  they  become 
malleable. 

The  manufacture  of  malleable  castings  embraces  the 
following  stages  : — 

Making  the  Pattern. — The  moulds  are  of  green  or  of  dry 
sand. 

Melting  the  Metal. — The  metal  is  melted  in  graphite 
crucibles,  or,  in  some  cases  where  the  castings  are  large,  in 
cupolas,  and  cast  in  the  moulds.  A  special  kind  of  pig  iron 
is  required,  and  suitable  scrap  is  melted  with  it. 

Cleaning  the  Castings. — When  cold,  the  castings  are 
cleaned  by  being  turned  over  many  times  in  a  horizontal 
rotating  barrel  designed  with  sharp  corners.  The  castings 
rub  against  each  other,  and  the  sharp  corners  hasten  the  de- 
taching of  the  sand. 

Annealing  the  Castings. — The  articles  to  be  annealed  are 
carefully  packed  in  red  hematite  iron  ore  in  suitable  vessels, 
and  are  carefully  heated  and  allowed  to  cool  down  slowly. 

The  ore,  having  been  crushed  as  small  as  peas,  is  sifted,  and 
a  mixture  of  two  or  three  parts  of  old  ore  with  one  part  of 
new  ore  is  used.  When  new  ore  is  used  alone  the  "annealing" 
action  is  too  keen.  The  containing  vessels  are  crucibles  or 
"pots,"  or  cast-iron  boxes  called  "saggers,"  or  wrought-iron 
boxes. 


168 


IRON    AND    STEEL    MANUFACTURE. 


The  pots,  or  boxes,  which  may  be  square  or  circular  in  plan, 
are  cast  from  a  special  mixture  of  white  iron  and  scrap,  and 
they  vary  in  capacity  according  to  the  size  of  the  castings  to 
be  annealed  in  them.  For  certain  castings  the  ore  and  pot 
together  may  weigh  2£  cwts.,  the  castings  for  annealing  f  cwt. 
When  the  packing  of  a  pot  or  box  is  completed  the  lid  is  luted 
on.  The  packed  boxes  are  then  placed  in  the  furnace. 

The  furnaces  are  coal-fired  or  gas-fired.  Some  are  rectangular 
in  plan,  with  dome-shaped  roofs.  They  are  built  in  rows,  each 
furnace  being  connected  with  a  flue  leading  to  a  stack.  Such 
a  furnace  is  shown  in  fig.  78.*  The  middle  portion  of  the 

bed  is  raised,  thus  providing  two 
passages  down  the  sides  for  the 
fires.  The  boxes  containing  the 
castings  are  placed  on  this  raised 
floor,  three  or  four  in  each  pile,  the 
joints  between  them  being  sealed 
with  fireclay  or  wheelswarf,  and  the 
top  box  completely  covered  with 
the  same  substance.  Each  furnace 
holds  from  12  to  20  boxes.  The 
most  important  articles  are  placed 
in  the  centre  pots. 

During  Bannister's  investigations 
from  10  to  20  boxes  were  placed 
»  a  furnace,  and  the  temperature 
maintained  was  from  1,000  0. 
(1,832°  F.)  to  1,100°  C.  (2,012°  F.)  during  days,  the  fires 
being  damped  down  for  nights,  thus  giving  a  bright  red  heat 
during  days,  and  a  dull  red  during  nights.  The  furnace 
was  fired  from  five  to  nine  days,  and  allowed  to  cool  down 
for  two  days. 

In  Royston's  investigations  f  the  pots,  60  in  number,  were 
charged  into  a  black-hot  furnace  which  had  just  been  emptied. 
The  door  was  luted  and  firing  commenced.  The  temperature 
of  the  furnnce  on  the  second  day  was  750°  0.,  on  the  third  day 

*  From  paper  by  C.  0.  Bannister,  A.B.S.M.,  Inst.  Mech.  Engineers, 
January,  1904. 
t  Journal  of  the  Iron  and  Steel  Institute,  i.,  1897. 


MALLEABLE    CASTINGS. 


169 


it  was  860°  C.,  while  on  the  fourth,  fifth,  and  sixth  days  the 
furnace  heat  did  not  vary  more  than  40°  from  860°  C.  As 
the  pots  became  red  hot,  copious  jets  of  flame  were  emitted 
and  burned  with  a  blue  flame,  which  may  be  accepted  as 
evidence  of  the  escape  of  carbon  monoxide  (CO)  from  within 
the  pots.  The  coal  used  amounted  to  If  tons  per  ton  of 
metal  annealed.  When  the  furnace  had  cooled  sufficiently 
the  pots  were  withdrawn.  Three  days,  instead  of  seven,  may 
suffice  for  some  kinds  of  work. 

The  boxes  are  in  due  course  unpacked,  the  castings  are 
cleaned,  and  are  then  ready  for  the  market. 

Malleable  castings,  if  in  thin  sections,  can  be  welded  The 
castings  are  not  brittle,  as  they  were  before  annealing,  but  are 
generally  tough  enough  to  stand  bending  into  a  U  shape  even 
when  cold.  They  are  cleaned,  and  are  then  ready  for  the 
market. 

Consideration  of  Composition  and  Changes. — The  pig  iron 
used  should  be  low  in  silicon,  phosphorus,  and  manganese,  as 
these  remain  unaffected  during  annealing  and  their  presence 
in  the  finished  casting  is  harmful.  Manganese  and  sulphur 
retard  the  annealing.  The  pig  iron  used  sometimes  contains 
over  *3  per  cent,  of  sulphur,  which  is  not  desirable.  The 
best  "  metal "  for  the  purpose  is  refined  white  hematite  pig 
iron  along  with  good  scrap. 

TABLE  OF  COMPOSITION. 


Refined 

Constituents. 

Chemical 
Symbols. 

White 
Hematite 
Pig  Iron 

White 
Hematite 
Pig  Iron 
after 

Castings 
after  being 
Annealed. 

Melting. 

Melting. 

Graphitic  carbon 
Combined  carbon 

C 
C 

0-61 
3-33 

0-19 
3-69 

1-56 
0-74 

Total  carbon, 

C 

3-94 

3-88 

2-30 

Silicon, 

Si 

0-61 

0-57 

0-57 

Sulphur, 
Phosphorus, 
Manganese, 

s 
p 

Mn 

0-03 
0-044 
0-112 

o-io 

0-045 

0-043 

0-057 
0-045 
0-043 

Iron  (by  difference), 

Fe 

A 

A 

A 

100-00 

100-00 

100-00 

170  IRON    AND    STEEL    MANUFACTURE. 

The  metal  takes  up  sulphur  during  melting,  whether  in  a 
crucible*  or  in  a  cupola.*  Royston  found  the  following 
percentages  of  sulphur: — 

Before  melting  =  '031. 

After  melting  in  an  open  crucible  =  '096. 
After  melting  in  a  cupola  =  '161. 

The  coke  used  contained  1*60  per  cent,  of  sulphur,  which  is 
a  high  percentage. 

During  annealing  the  changes  induced  are : — 

(a)  Change  in  the  condition  of  some  of  the  carbon ; 

(b)  Reduction  in  the  amount  of  carbon ; 

(c)  Reduction  in  the  amount  of  sulphur ;  and 

(d)  Reduction  of  some  oxide  of  iron  to  the  metallic 

state. 

In  Bannister's  experiments  the  sulphur  was  diminished 
•03  per  cent.  The  used  ore  has  been  found  to  contain 
pellets  of  iron,  and  sulphur  has  been  taken  up  by  the  ore 
when  the  castings  were  not  low  in  sulphur  before  annealing, 
The  spent  ore  also  contains  carbon  derived  from  the  castings. 
About  half  of  the  carbon  is  withdrawn  from  the  iron,  a  change 
which  is  quite  the  reverse  of  that  resulting  from  the  cementa- 
tion process.  Most  of  the  remaining  carbon  is  changed  from 
the  combined  state  to  fine-grained  graphite. 

The  combined  carbon  in  the  pig  iron  lowers  its  melting 
point,  increases  its  fluidity,  and  enables  a  clean,  sharp  casting 
to  be  made.  The  amount  of  combined  carbon  which  is  left  in 
the  finished  casting  does  not  impair  its  malleability  too  much. 

*  For  description  of  a  crucible  see  p.  42,  and  of  a  cupola  see  p.  150. 


171 


CPJAPTEB,   XVII. 
CASE-HARDENING. 

SOMETIMES  it  is  requisite  that  wrought-iron  articles  should  be 
hardened  on  the  surface  and  a  little  beneath.  The  most 
convenient  known  method  of  hardening  is  by  adding  carbon 
and  then  quickly  quenching  from  a  suitable  temperature. 

In  case-hardening,  the  carbon  addition  is  effected  by  packing 
the  articles  in  a  box  containing  a  sufficiency  of  substances 
which  are  rich  in  carbon  and  in  nitrogen.  The  most  com- 
monly-used substances  are  leather  cuttings,  horse-hoof  pairings, 
potassic  ferro-cyanide  (popularly  called  prussiate  of  potash), 
and  bone  charcoal.  The  articles  are  embedded  in  one  or 
other  of  the  above-named  substances.  The  lid  is  then  closely 
luted  with  fireclay.  The  box  and  contents  are  placed  in  a 
furnace  which  is  raised  to  a  cherry -red  heat  (about  860°  C.) 
and  maintained  at  that  temperature  for  12  or  even  up  to 
24  hours,  according  to  the  depth  of  hardening  wanted.  The 
box  is  allowed  to  cool  down  till  the  contents  are  cold  enough 
to  bear  removal — although  still  red  hot — when  they  are 
plunged  into  cold  water.  If  cooled  too  much  before  removal 
from  the  box,  the  articles  are  reheated  and  suddenly  quenched. 

Those  parts  which  are  not  to  be  case-hardened  are  carefully 
covered  with  fireclay  before  placing  in  the  box  in  which  the 
carbonisation  is  carried  on. 

The  smooth  wearing  parts  of  axles  are  covered  with  a 
leather  sheath  and  placed  in  a  furnace.  When  the  part  which 
is  in  contact  with  the  leather  is  judged  to  have  taken  up 
enough  carbon  it  is  withdrawn  from  the  furnace  and  quenched. 
The  other  end  is  then  similarly  treated. 

When  wrought  iron — which  does  not  contain  much  carbon 
— is  embedded  in  charcoal  and  steadily  heated  for  several 
days  (see  p.  39)  to  a  high  temperature,  carbon  penetrates 


172  IRON    AND    STEEL   MANUFACTURE. 

right  to  the  heart  of  the  wrought  iron  and  converts  it  into 
steel.  In  case-hardening,  the  conversion  to  steel  is  superficial, 
and  as  it  is  practised  on  articles  of  finished  shape  they  must 
be  embedded  in  a  substance  which  quickly  yields  carbonaceous 
material  at  such  a  moderate  temperature  as  will  not  cause 
distortion  of  the  articles. 

In  distinct  contrast  to  these  processes,  by  which  iron  is 
caused  to  take  up  carbon,  is  the  method  of  treating  iron 
castings  so  that  the  carbon  is  changed  and  withdrawn,  and 
some  of  the  qualities  of  wrought  iron  conferred  on  them. 


ITS 


Having  in  the  foregoing  pages  dealt  with  tho 
selection  and  working  of  pig  irons  to  achieve 
desired  ends,  we  are  now  in  a  position  to  proceed 
to  the  consideration  of  the  composition  of  iron 
ores  and  their  treatment  in  the  production  of  pig 
iron  suited  to  various  requirements. 


174 


CHAPTER   XVIIL 

IRON  ORES:  THEIR  COMPOSITION,  CHARACTERS, 
AND  DISTRIBUTION.  KIND  OF  PIG  IRON  PRO- 
DUCED FROM  EACH. 

ANY  large  quantity  of  naturally-deposited  matter  containing 
metals — either  in  the  free  state  or  in  chemical  combination — 
may  be  considered  an  ore  if  the  metals  are  present  in  sufficient 
quantity  and  in  such  a  state  as  to  permit  of  profitable  extrac- 
tion. In  ores  the  metals  are  generally  in  combination  with 
oxygen  or  sulphur,  or  they  exist  as  carbonates  or  silicates. 
Less  frequently,  the  metal  or  metals  are  in  combination  with 
chlorine  or  some  other  non-metal.  When  an  ore  contains 
metal  which  is  not  in  chemical  combination  with  a  non-metal 
it  is  said  to  be  "  native."  Certain  ores  are  very  complex,  and 
some  contain  metals  which  are  not  easily  separated  during 
extraction.  Ores  which  occur  near  the  surface  of  the  earth 
are  dug  or  quarried;  those  which  are  found  at  lower  depths 
are  mined. 

Iron  Ores. — When  iron  is  exposed  to  ordinary  moist  air 
it  "  rusts " — the  bright,  strong  metal  is  converted  into  a 
voluminous,  crumbling  mass  of  earthy-looking  matter  quite 
devoid  of  the  characteristic  good  qualities  which  iron  possesses. 
Some  deposits  of  iron  ore  may  be  looked  upon  as  iron  rust, 
more  or  less  altered  in  composition  by  heat,  and  which  have 
become  naturally  mixed  with  widely- vary  ing  amounts  of  other 
matter,  such  as  silica,  clay,  calcic  phosphates,  &c.  The  "  other 
matter"  constitutes  the  gangue  of  the  ore,  and  the  gangue 
usually  requires  some  flax  to  accompany  it  in  the  blast  fur- 
nace. For  example,  silica  (Si02),  which  forms  such  a  large 
percentage  of  the  gangue  of  many  ores,  is  quite  infusible  even 
at  the  very  high  temperature  of  the  blast  furnace,  but  at  that 
temperature  the  silica  may  be  caused  to  enter  into  chemical 
combination  with  the  flux  so  as  to  form  a  fluid  compound 
and  be  tapped  out  as  slag. 


IRON    ORES.  175 

The  ores  of  iron  which  are  smelted  are  all  essentially  oxides 
of  iron  mixed  with  gangue,  and  they  all  contain  phosphorub 
They  may  be  conveniently  classed  thus  : — 

Ferrous  ores — 

Blackband  ironstone, 
Clayband  ironstone. 
Cleveland  ironstone. 
Spathic  iron  ore. 

Ferric  ores — 

Red  hematite. 
Brown  hematite, 

Ferrous-ferric  ores — 
Magnetite. 
Franklinite. 
Ilmenite. 

Ferrous  Ores  consist  essentially  of  ferrous  carbonate 
(FeO,C02)  with  other  matters.  Clayband  ironstone  contains 
ferrous  carbonate  and  clay.  Blackband  ironstone  contains 
coaly  matter  in  addition.  Cleveland  ironstone  contains  ferrous 
carbonate  and  clay,  and  is  more  highly  phosphoric  than  the 
others.  Spathic  ore,  or  siderite,*  sometimes  contains  a 
notable  amount  of  manganese  and  much  less  phosphorus  than 
the  other  ferrous  ores.  It  is,  as  its  name  indicates,  sparry 
or  crystalline. 

Ferric  Ores  consist  essentially  of  ferric  oxide  (Fe903)  with 
other  matters.  The  typical  red  hematite  of  Cumberland 
and.  North  Lancashire  is  remarkably  low  in  phosphorus 
and  sulphur.  Of  this  class  of  ore  there  are  several  varieties. 
Red  hematite  is  largely  mined  in  small  fragments,  which 
are  ruddy  -  coloured,  have  a  greasy  feel,  and  stain  the 
hands  when  touched.  It  also  exists  in  iron-grey  masses, 
which,  where  weathered,  are  red-coloured.  This  variety  is 
known  as  pencil  ore,  from  the  facility  with  which  it  splits 
into  long  fragments,  which  are  sometimes  used  for  marking 
sandstones.  Kidney  ore  occurs  in  lumps  with  rounded 
surfaces  which  are  dark  steel-grey  in  colour.  Another  kind 

*  From  a  Greek  word  signifying  iron. 


176  IRON    AND    STEEL    MANUFACTURE. 

is  found  like  flattened  grains,  and  is  known  as  lenticular 
(pea-shaped)  ore.  Specular  ore  is  of  a  bluish-black  colour 
and  sparkles  from  many  crystals  on  its  surface. 

Ferric  ores,  which  contain  a  notable  quantity  of  alumina, 
are  shipped  from  the  north  of  Ireland  to  the  nearest  districts 
where  hematite  ores  are  smelted.  They  are  known  in  the  trade 
as  Aluminous  ores,  Antrim  ores,  Belfast  ores,  and  Irish  ores, 
Occasionally  they  are  washed  before  being  shipped. 

Brown  Hematites  may  be  fairly  compact  or  moderately 
soft.  In  colour,  ores  of  this  class  vary  from  rich  brown  to 
yellow.  They  consist  essentially  of  ferric  oxide,  with  about 
10  per  cent,  or  so  of  combined  water.  Some  kinds  contain  as 
little  phosphorus  as  good  red  hematite  does,  while  others  are 
highly  phosphoric  and  do  not  contain  a  high  percentage  of  iron. 

Ores  of  the  Ferrous-ferric  Type  do  not  occur  in  notable 
quantities  in  the  British  Isles,  but  ores  of  this  class,  which 
are  found  in  other  countries,  are  of  considerable  importance. 

Magnetite  is  found  in  masses  in  Sweden.  The  ore  is 
frequently  rich  in  iron  and  is  usually  low  in  phosphorus  and 
sulphur.  It  is  generally  dark  and  hard.  A  magnet  will  cling 
to  a  mass  of  the  ore  and  can  lift  small  fragments  of  it. 

Other  Sources  of  Iron  are : — 

Burnt  Pyrites. — This  is  the  residue  from  the  treatment  of 
pyrites — an  ore  containing  iron  and  sulphur,  and  often  a 
small  quantity  of  copper.  In  the  first  place  the  ore  is  broken 
into  smaller  lumps,  when  necessary,  and  slowly  burned ;  the 
resulting  sulphury  gas  (sulphur  dioxide)  is  led  into  huge  leaden 
chambers  where  sulphuric  acid  (commonly  called  vitriol)  is 
made.  If  the  "burnt  pyrites"  contains  enough  copper  to  more 
than  cover  the  cost  of  its  extraction  it  is  crushed  smaller  than 
peas,  mixed  with  salt,  carefully  roasted,  and  then  leached 
(soaked)  in  water  to  dissolve  the  copper  compound.  The 
residual  iron — which  was  oxidised  during  the  burning  of  the 
sulphur — has  a  dark  purple  colour,  and  is  generally  known  in 
iron  works  as  "Purple  Ore"  or  "Blue  Billy." 

Burnt  pyrites  and  purple  ore  have  recently  become  of 
considerable  importance  as  sources  of  iron. 

Flue  Cinder,  which  is  the  slag  from  certain  reheating 
furnaces,  is  also  used  for  the  production  of  certain  classes 
of  pig  iron. 


IRON    ORES. 


177 


Puddlers'  Cinder,  or  Puddlers'  Tap  (see  p.  25),  is  smelted 
along  with  local  ores,  in  blast  furnaces,  for  the  production  of 
cinder  pig.  It  yields  a  highly-phosphoric  pig  iron,  which  is 
well  suited  for  the  basic  Bessemer  process. 

Mineral  phosphates  (apatite,  &c.)  are  occasionally  charged 
into  blast  furnaces  to  increase  the  percentage  of  phosphorus 
in  the  pig  iron  for  basic  steel-making. 

The  following  figures  represent,  in  round  numbers,  the 
composition  of  some  of  the  chief  iron  ores  : — 


Constituents. 

Chemical 
[formula?. 

FERROUS  ORES. 

Blackband 
Ironstone 
(Staffs.) 

Clayband 
Ironstone 
Ayrshire) 

Cleveland 
ronstone. 

Spathic 
Ore. 

Ferrous  oxide,    . 

FeO 

42-0 

40-0 

38-0 

49-33 

Ferric  oxide, 

Fe,03 

6-0 

... 

6-0 

0-8 

Manganous  oxide, 

MnO 

3-0 

1-0 

0-5 

2-2 

Silica, 

Si02 

1-5 

10-5 

12-0 

4-0 

Alumina,    . 

A  LA., 

0-3 

5-0 

11-0 

0-7 

Lime, 

CaO 

4-0 

5-0 

5'5 

3-3 

Magnesia.  . 

MgO 

2/0 

3-0 

3-5 

2-6 

Phosphoric  acid. 
Sulphur,     . 

PA 

s 

0-7 
0-5 

1-3 
0-2 

1-5 
03 

0-03 

0-04 

Carbon  dioxide, 

C02 

26-0 

3TO 

21-0 

37-0 

Organic  matter, 

... 

'14-0 

3-0 

0-7 

Combined  water, 
Total, 
Metallic  iron,     . 

H,0 

... 

100-0 

100-0 

1000 

100-00 

36-87 

31-11 

33-75 

38-93 

Phosphorus, 

... 

0-31 

0-57 

0-65 

0-013 

lli 


178 


IRON    AND    STEEL    MANUFACTURE. 


OVtACTll 

FERRIC  ORBS. 

FERROUS-FERRIC 
ORES. 

Constituents. 

unerni- 
cal 
For- 

English 
fied 

Spanish 

English 
Brown 

mulae. 

Hema- 

Brown 

Hema- 

Magnetite. 

Magnetite. 

tite. 

Hematite. 

tite. 

Sweden. 

Sweden. 

Cumber- 

Bilbao. 

North- 

land. 

ampton. 

Ferrous  oxide,     . 

FeO 

1-0 

23-00 

27-00 

Ferric  oxide, 

Fe203 

86<)0 

78-00 

63-0 

52-00 

60-00 

Manganous  oxide, 
Silica, 

MnO 
Si(X> 

0-25 
9-00 

1-00 
9-00 

0-2 
9-0 

2-00 
8-00 

o-io 

5-00 

Alumina,     .      ,'.• 

AlA 

0-50 

1-00 

6-0 

2-00 

1:00 

'Lime,  .         .      x-.' 

CaO 

3-00 

0-70 

3-0 

6-00 

3-00 

Magnesia,    . 

MgO 

1-00 

0-20 

0-5 

5-00 

2-00 

Phosphoric  acid, 

P20S 

0-03 

0-04 

1-8 

0-02 

2-00 

Sulphur, 

8 

0-04 

0-03 

0-2 

0-02 

o-oi 

Carbon  dioxide,  . 
Organic  matter,  . 

C02 

... 

2-0 

1  2-00 

... 

Combined  water, 

H^O 

... 

10  -00 

13-6 

if°  ,  "-V  v" 

Total, 

... 

99-82 

99-97 

99-7 

100-04 

100-11 

Metallic  iron, 

60-20 

54-60 

44-88 

54-29 

63-00 

Phosphorus, 

0-013 

0-017 

0-79 

0-009 

0-87 

For  analyses  of  other  ores,  see  pp.  242,  243,  and  244. 


THE  SUPPLY  OF  ORES  FOR  THE  BRITISH  IRON  TRADE. 

As  Great  Britain  has  been  for  a  long  period  the  abode  of  an 
active  iron-producing  people,  the  working-out  or  impoverish- 
ment of  certain  mining  districts  must  come  as  a  matter  of 
course.  At  present,  about  twelve  million  tons  of  iron  ores  are 
annually  raised  in  Great  Britain,  and  about  six  million  tons 
are  imported. 

Kefl  Hematite  Ores  are  mined  in  that  part  of  the  north- 
west of  England  which  is  known  as  the  hematite  district — 
Cumberland  and  North  Lancashire. 

The  purer  varieties  of  Brown  Hematite  Ores  are  mined 
in  the  Forest  of  Dean,  on  the  Severn  estuary,  near  to  South 
Wales.  The  less  pure  (highly  phosphoric)  Brown  Hematite 
Ores  are  extensively  worked  in  Lincolnshire,  Leicestershire, 


IRON   ORES.  179 

and  Northamptonshire.  Some  of  the  ore  beds  consist  largely 
of  carbonate.  Considerable  quantities  are  quarried,  calcined, 
and  sent  into  Staffordshire. 

Spathic  Ores. — Ores  of  this  class  were  mined  in  Weardale 
(County  Durham),  from  the  Brendon  Hills  (Somersetshire), 
and  from  Exmoor  (Devonshire).  The  latter  contained  a 
notable  percentage  of  manganese. 

Blackband  Ironstone  is  still  mined  towards  the  east  of 
Scotland  and  in  North  Staffordshire. 

Cleveland  Ironstone  exists  in  large  quantities  in  the  hilly 
district  of  Cleveland,  in  the  north-east  of  Yorkshire. 

Clayband  Ironstone  was  formerly  a  chief  source  of  British 
iron :  at  present  it  is  only  mined  in  a  few  districts  where  the 
deposits  are  comparatively  thick  and  rich.  It  is  still  worked 
to  a  large  extent  in  Ayrshire,  Yorkshire,  Derbyshire,  Stafford- 
shire, and  East  Worcestershire.  In  other  districts  the  "  coal 
balls "  met  with  in  coal-mining  are  often  saved  for  use  in 
blast  furnaces. 

Imported  Iron  Ores. — Large  and  increasing  quantities  of 
iron  ores  are  brought  from  abroad  at  comparatively  low 
freights.  The  imported  ores  comprise: — Manganese  ores  from 
India  and  elsewhere,  chrome-iron  ore  from  Russia  and  other 
countries,  specular  ore  from  Elba,  in  the  Mediterranean; 
iron  ores  from  Greece  and  the  south  of  Spain;  and,  in  much 
larger  quantities,  brown  hematite  and  calcined  carbonate  from 
the  north  of  Spain.  From  Dunderland,  in  Norway,  immense 
supplies  of  concentrated  ores  may  be  obtained. 

Imported  ores  are  smelted  in  districts  at  or  near  the  sea- 
board where  good  fuel  is  cheap.  Of  these  the  most  convenient 
are  South  .Wales,  Middlesbrough  (in  the  north  of  Yorkshire), 
and  the  district  around  Glasgow,  which  has  the  advantage  of 
a  waterway — the  Clyde — a  river  which  has  been  persistently 
deepened  with  commendable  enterprise.  To  North  Lanca- 
shire and  Cumberland,  where  rich  deposits  of  hematite  ores 
have  been  found,  the  purer  varieties  of  hematite  ores  are  also 
imported,  and  smelted  along  with  the  local  ores.  Durham 
coke  is  much  used  in  the  blast  furnaces  in  the  hematite 
district  in  the  north-west  of  England. 


180  IRON   ANT)    STEEL    MANUFACTURE. 

The  purpose  for  which  a  pig  iron  is  best  suited  is  decided, 
in  large  measure  at  least,  by  the  percentage  of  phosphorus 
it  contains.  With  few  exceptions  of  small  importance,  nearly 
all  the  phosphorus  which  is  present  in  the  ore,  the  flux,  and  the 
fuel  used  in  smelting  goes  into  the  pig  iron*  The  kind  of  pig 
iron  made  in  any  district  will  depend  very  much  on  the 
class,  or  grade,  of  ore  which  can  be  had  there  at  a  paying 
price. 

The  Production  of  Hematite/ Pig  Iron — known  also  as 
Bessemer  Pig  Iron — for  use  in  the  acid  Bessemer  and  the  acid 
Siemens  processes  is  conducted  in  Cumberland  and  in  North 
Lancashire  where  good  hematite  ores  are  mined,  and  which 
are  supplemented  by  hematite  ores  imported  from  Spain. 
The  chief  drawback  to  that  district — apart  from  royalties, 
&c. — is  the  want  of  a  good  cheap  fuel.  The  railway  charge 
for  the  carriage  of  coke  is  a  heavy  burden.  In  South  Wales, 
where  good  coal  is  abundant  and  fair-quality  coke  is  cheap, 
brown  hematite  ores  mined  in  the  Forest  of  Dean  are  smelted, 
as  are  also  hematite  ores  from  the  north-west  of  England  and 
from  Spanish  ores.  In  the  district  of  which  Glasgow  is  the 
commercial  centre,  a  mixture  of  English  and  Spanish  hematite 
ores  is  smelted.  The  aluminous  ores  from  the  North  of 
Ireland  are  also  used  in  the  blast  furnaces  producing  hematite 
pig  iron  in  Scotland  and  in  the  English  hematite  districts, 
both  of  which  are  convenient  to  Ireland.  At  and  near 
Middlesbrough,  adjoining  the  district  where  perhaps  the 
finest  coke  in  the  world  is  made,  hematite  ores  from  Spain 
and  from  the  north-west  of  England  are  smelted  together. 
It  is  also  well  situated  for  dealing  with  Swedish  ores  and  the 
Dunderland  ores,  which,  as  concentrated,  are  pure  enough  for 
making  the  best  quality  of  hematite  pig  iron. 

The  •Production  of  Pig  Irons  for  use  in  Forges  and 
Foundries  is  a  feature  of  those  districts  where  clayband  or 
impure  brown  hematite  ores  exist.  They  are,  of  course,  made 
mostly  from  the  local  ores. 

Basic  Pig  Iron,  being  even  more  highly  phosphoric  than 
the  foregoing,  is  made  in  or  near  localities  in  which  puddling 

*  The  phosphorus  exists  as  phosphorus  pentoxide  (P205),  or  phosphoric 
acid  as  it  is  more  often  called,  in  all  iron  ores  and  solid  fuels. 


[To  face  p.  180. 


Reduced  from  a  diagram  in  "  Caseier'g  Magazine. 


IRON    ORES.  181 

is,  or  has  been,  a  staple  industry,   because  there   puddlers' 
cinder  may  be  had  cheaply  and  in  abundance. 

Ores  used  for  Various  Kinds  of  Pig  Iron. — The  purest 
Swedish  pig  irons  are  smelted  from  pure  magnetites,  with 
charcoal  as  fuel.  Pig  iron  smelted  from  such  ores,  with  such 
pure  fuel  as  charcoal,  is  remarkably  low  in  both  phosphorus 
and  sulphur. 

Bessemer  Pig  Iron  is  made  from  hematite  or  other  ores, 
such  as  magnetites  and  Spanish  carbonates,  which  are 
low  in  phosphorus.  The  fuel  and  the  flux  require  to  be 
carefully  selected.  Bessemer  pig  iron,  or  hematite  pig  iron  as 
it  is  also  called,  is  used  for  the  acid  Bessemer  and  the  acid 
Siemens  processes;  and  sometimes,  although  not  always 
judiciously,  for  superior  castings.  White  hematite  pig  iron 
is  used  for  the  manufacture  of  malleable  castings. 

Foundry  and  Forge  Pig  Irons  are  made  from  blackband, 
clay  band,  and  Cleveland  ironstones.  Phosphoric  hematite 
and  other  ores  are  also  used. 

All-mine  Pig  Irons  are  made  from  ores.  Cinder  pig  irons 
are  made  from  a  mixture  of  puddlers'  tap  (tap  cinder)  and 
local  ores. 

Basic  Pig  Iron  is  made  in  Lincolnshire  from  ores  obtained 
in  that  county ;  in  other  districts  it  is  made  from  puddlers' 
tap  and  clayband,  Cleveland,  or  impure  brown  hematite  ores, 
and  some  manganese  ore  and  mineral  phosphates  from  abroad. 
The  proportion  of  puddlers'  tap  used  is  sometimes  considerable ; 
the  ores  used  are  mined  or  quarried  not  far  from  the  works, 
with  the  exception  of  the  manganese  ore,  which  is  always 
foreign. 


182 


CHAPTER   XIX. 
PREPARATION   OF   ORES   FOR   SMELTING. 

SOME  iron  ores  require  preparation  before  being  charged  into 
the  blast  furnace.  The  preliminary  treatment  may  consist  of 
breaking  or  crushing  lumpy  ores  to  suitable  size.  Or,  on  the 
oilier  hand,  the  ores  which  are  in  pellets,  or  even  in  a  finer 
state  of  division,  are,  with  advantage,  pressed  into  blocks 
or  briquettes  and  "burnt,"  so  that  the  fine  ore  will  not 
be  so  liable  to  be  forced  out  of  the  blast  furnace  with  the 
exit  gases,  or  be  so  likely  to  "  gob  "  the  furnace  or  derange  the 
working  by  hindering  the  free  course  of  the  gases.  Many  ores 
are  delivered  with  such  a  large  proportion  of  "  smalls  "  as  to 
cause  trouble  to  managers  and  workmen. 

Some  poor  ores  are  subjected  to  magnetic  concentration. 
Such  ores  are  crushed  to  powder,  and  caused  to  fall  in  a  fine 
stream  near  to  electro-magnets.  The  magnetic  influence  draws 
aside  nearly  all  the  metallic  portion,  which  falls  into  a  truck 
apart  from  the  bulk  of  the  gangue.  The  concentrated  iron 
oxide  is  then  made  into  blocks  in  the  manner  described  above. 

Besides  the  breaking  up,  or  the  binding,  of  iron  ores,  other 
treatment  is  sometimes  called  for.  Some  iron  ores  are  so 
firmly  united  in  the  mine  to  layers  of  shale  that  separation  of 
one  from  the  other  is  difficult.  By  weathering — that  is,  by 
exposing  to  atmospheric  influences  for  a  time — the  shale  may 
be  easily  split  off.  Weathering  may,  to  a  slight  extent,  cause 
the  removal  of  sulphur  from  certain  ores. 

All  ferrous  ores  are  subjected  to  preliminary  heat  treatment 
with  access  of  plenty  of  air.  This  roasting  process  is  known 
in  the  trade  as  calcination  or  burning. 

The  effects  of  calcination  are: — 

The  lower  iron  oxide  (ferrous  oxide)  is  changed  into 
the  more  highly  oxidised  ferric  oxide,  and,  at  the  same 
time,  the  oxide  of  manganese  which  is  present  combines 
with  more  oxygen. 


PREPARATION    OF   ORES    FOR   SMELTING. 


183 


Carbon  dioxide  is  driven  off. 

Moisture  is  driven  off. 

Organic  matter  is  driven  off. 

Carbon  monoxide  is  occasionally  given  off  in  small 
amount. 

Sulphur  may  be  driven  off  in  perceptible  amount, 
especially  if  calcination  is  conducted  slowly  at  a  proper 
temperature  and  with  access  of  abundance  of  air. 

The  chief  chemical  changes  may  be  represented  by  the 
equations — 


4FeCO, 


0, 


2Fe2Oa 


4CO, 


6MnC03         +          02 
Manqanous  \        , 

and    ox^en 


carbonate 


2Mn304  +         6COa 

(     manganoso-     }        -,  (  carbon 
\  manganic  oxide  }  and  \  dioxide. 


The  chemical  changes  which  take  place  may  be  further 
traced  in  the  following  table  :  — 


Chemical 

Cleveland 

Ironstone. 

Constituents. 

Formate. 

Before 
Calcination. 

After 
Calcination. 

Ferrous  oxide,  .     -  .        .         ,v 

FeO 

35-00 

Ferric  oxide, 

Fe203 

5-55 

58*43 

Manganous  oxide,      .         .   /••.  '-»' 
Manganoso-manganic  oxide, 
Silica,        .... 

MnO 
Mn304 

Si02 

0-41 
10-97 

6-56 
14-33 

Alumina,  .... 

A1203 

10-22 

13-34 

Lime,         .        .        .    '     .' 

CaO 

4-84 

6-37 

Magnesia,  ....  ;   ,  ,  '  ,, 

MgO 

3-50 

4-55 

Sulphur,    . 

S 

0-25 

0-81 

Phosphoric  acid, 
Carbon  dioxide, 

PA 
C02 

1-25 
18-01 

1-67 

Combined  water,  moisture,  and 

carbonaceous  matter,     .      '  t  . 

... 

10-10 

... 

Total,       .'  ,     v  '     V 

100-12 

100*06 

Metallic  iron,     .         .         .         . 

Fe 

31-11 

40-90 

184  IRON    AND    STEEL   MANUFACTURE. 

Advantages  of  Calcination. — Peroxidised  iron  (ferric  oxide) 
works  better  in  the  furnace ;  it  does  not  enter  into  chemical 
union  with  the  silica  in  the  ore  and  "scour"  into  the  slag. 
The  driving  off — outside  the  blast  furnace — of  the  carbon 
dioxide  which  is  always  present  in  ferrous  ores  prevents  the 
overpowering  of  the  reducing  gases  which  require  to  be  in 
excess  in  the  blast  furnace.  The  vast  volume  of  gases  which 
issue  from  the  blast  furnace  are  increased  in  value,  for  power 
purposes,  by  containing  that  lesser  quantity  of  carbon  dioxide. 
In  like  manner  the  preliminary  driving  away  of  moisture  is  an 
advantage.  Calcined  ores,  being  more  porous,  permit  the 
blast-furnace  gases  to  more  readily  permeate  them,  and  thus 
the  reducing  action  is  hastened. 

The  shrinkage  which  takes  place  during  calcination  is  a 
double  advantage.  In  the  first  place,  a  greater  weight  of  ore 
can  be  kept  in  the  furnace,  and  there  is  produced  an  increased 
weight  of  pig  iron,  per  day,  in  consequence.  And,  in  the 
second  place,  the  furnace  works  more  smoothly  than  with  an 
ore  which  would  shrink  during  an  early  stage  of  the  smelting. 

Brown  hematite  ores,  which  are  ferric  ores  with  combined 
water,  are  sometimes  "  calcined  "  to  drive  off  the  water  they 
contain,  as  well  as  the  carbonic  acid  which  is  often  present. 

Bed  hematite  ores  are  not  subjected  to  calcination. 

Calcination  may  be  conducted  in  open  heaps,  in  stalls,  or  in 
kilns.  To  carry  on  calcination  in  open  heaps  a  piece  of 
suitable  ground  is  selected,  a  layer  of  small  lumps  of  ore  is  laid 
down,  and  some  coal  is  placed  over  it.  Then  alternate  layers, 
or  a  mixture  of  ore  with  about  8  per  cent,  of  coal  slack,  are 
heaped  up  to  a  height  of  about  6  feet,  so  as  to  form  a  mound, 
or  heap,  which  may  be  of  considerable  length  and  breadth. 
The  dimensions  differ  in  different  districts,  and  the  amount  of 
coal  is  varied  to  suit  the  nature  of  the  ore  and  the  conditions 
of  working.  Owing  to  the  heat  generated  by  the  further 
oxidation  of  the  ferrous  and  manganous  oxides,  it  is  not 
necessary  to  use  much  fuel.  Blackband  ores  contain  more 
combustible  (bituminous)  matter  than  is  needed  to  compL-te 
the  calcination,  the  pieces  are  well  burned,  and,  in  many 
instances,  show  signs  of  fusion. 

The  fuel  is  kindled  at  one  end  of  the  heap,  and  calcination 
is  allowed  to  proceed  slowly,  the  "  burning  "  of  a  heap  occupy- 


PREPARATION    OP    ORES    FOR    SMELTING.  185 

ing  a  few  weeks.  Calcination  in  open  heaps  is  primitive,  is 
wasteful  of  fuel,  and  the  costs  for  handling  are  high.  As 
a  compensation,  much  of  the  sulphur  may  be  eliminated. 

At  Kilsyth,  Scotland,  the  blackband  ore  is  tipped  into 
heaps,  each  about  200  feet  long,  68  feet  wide,  and  about 
8  feet  high.  Each  heap  or  "  hearth  "  holds  about  3,000  tons 
of  raw  ore.  To  start  the  burning,  a  coal  fire  along  one  end  is 
lighted,  and  the  draught,  is  regulated  to  avoid  sintering  (the 
fusing  of  the  masses  to  each  other),  and  the  burning  continues 
for  five  or  six  weeks.  The  ore,  before  calcination,  contains 
34'1  per  cent,  of  iron,  and  afterwards  55*5  per  cent.  The 
ore  shrinks  to  half  its  original  bulk  during  calcination.  Three 
heaps  are  worked  at  the  same  time — one  being  filled,  one 
burning,  and  the  other  being  emptied.  Railway  lines  are  laid 
at  a  lower  level  for  the  trucks  into  which  the  calcined  ore — 
known  in  Scotland  as  "  char  " — is  loaded. 

Calcination  in  stalls  is  a  more  modern  method.  A  series  of 
stalls  consists  of  a  long  wall  from  which  other  walls  project  at 
right  angles,  so  that  each  compartment,  or  stall,  has  three 
walls.  Each  stall  is  filled  with  raw  ore  and  fuel,  and  the 
remaining  side,  or  rather  front,  is  temporarily  built  up  with 
bricks  or  with  lumps  of  ore.  If  of  brick,  air  holes  are  left  in 
the  front  wall.  The  fuel  is  kindled,  and  calcination  continues 
as  in  the  open  heaps. 

The  raw  ore  may  be  conveniently  delivered  from  trucks  on 
rails  which  are  placed  above  the  level  of  the  tops  of  the  stalls, 
and  the  calcined  ore  delivered  into  trucks  or  barrows  at  a 
lower  level. 

Calcination  in  stalls  is  under  better  control  than  in  heaps,  as 
the  air  can  be  more  easily  regulated.  The  fuel  consumed  is 
slightly  less. 

Calcination  in  kilns  is  a  more  convenient  and  economical 
method  than  either  of  the  foregoing.  A  calcining  kiln  is  an 
upright  shaft  furnace  which  is  open  at  the  top,  and  up  which 
a  current  of  air  passes  when  the  kiln  is  at  work.  There  is 
neither  forced  draught  nor  a  chimney. 

The  Scotch  kiln  is  built  of  firebricks.  The  raw  ore  and  the 
fuel  are  charged  at  the  top.  A  fire  having  been  kindled  in 
the  kiln  at  the  commencement  of  a  campaign,  the  fuel  which 
is  charged  with  the  ore  in  due  course  burns,  and  calcination 


186 


IRON    AND    STEEL    MANUFACTURE. 


goes  on.  The  calcined  ore  is  withdrawn,  through  openings 
near  the  bottom,  directly  into  trucks. 

The  inside  dimensions  of  the  kiln  represented  in  fig.  79 
are: — Height,  40  feet;  diameter  at  widest  part,  15  feet 
6  inches,  contracted  to  8  feet  3  inches  diameter  at  the  top  of 
the  cone  which  is  fixed  for  directing  the  ore  outwards. 

The  kiln  delivers  40  tons  of  calcined  ore  per  day,  and  the 
fuel  required  is  equal  to  3  per  cent,  of  the  weight  of  raw  ore. 


,-J 


Fig.  79.— Scotch  Calcining 
Kiln. 


Fig.  80.— Gjer's  Calcining 
Kiln. 


Gjer's  kilns  are  cylindrical  structures  of  firebrick,  sheathed 
in  metal  plates  and  set  on  short  cast-iron  columns.  The  ore 
which  is  to  be  calcined  is  conveyed  in  trucks  to  the  top,  and 
tipped,  along  with  the  necessary  fuel,  into  the  kiln.  The  air, 
for  maintaining  the  combustion  of  the  fuel  and  peroxidising 
the  metallic  oxides,  has  access  by  openings  in  the  tapered  part 
of  the  kiln,  and  also  by  the  openings  between  the  upper  and 
lower  parts  of  the  hollow  cone  which  is  set  centrally  at  the 


PREPARATION   OF   ORES   FOR   SMELTING.  187 

bottom.  By  having  the  central  opening  as  arranged,  dust, 
from  the  crumbling  of  the  ore,  is  not  likely  to  interrupt  the 
smooth  working  of  the  kiln. 

A  kiln  is  about  24  feet  in  diameter,  and  is  generally  about 
33  feet  high.  The  consumption  of  fuel  is  low,  1  ton  of  small 
coal  sufficing  for  the  calcination  of  25  tons  of  raw  Cleveland 
ore.  Other  ores  have  been  calcined  with  a  smaller  quantity  of 
fuel.  The  kiln  works  continuously. 

The  calcined  ore  is  withdrawn  through  openings,  into  the 
barrows  in  which  it  is  taken  to  the  top  of  the  blast  furnace. 


188 


CHAPTER     XX. 
THE   BLAST    FURNACE   AND   ITS   EQUIPMENT. 

THE  blast  furnace  is  a  most  compact  and  efficient  erection 
for  cheaply  and  quickly  treating  large  quantities  of  heavy 
materials.  In  it  iron  ore  is  dealt  with  at  a  high  temperature, 
and  the  iron  is  extracted. 

The  solid  materials  charged  into  the  blast  furnace  are — 

(a)  The  ore  from  which  the  iron  is  to  be  extracted, 

(b)  The  fuel  required  to  carry  on  the  work,  and 

(c)  The  flux,  which,  on  uniting  with  impurities  in  the  ore 

and  the  fuel,  causes  the  formation  of  fluid  compounds. 

These  solids  are  delivered  at  the  top  of  the  furnace  and  in 
due  course  descend.     A  strong  air  blast  is  injected  near  the 
bottom  of  the  furnace  where  the  fuel  is  burned. 
The  products  of  the  blast  furnace  are — 
(a)  The  pig  iron, 
(6)   Slag,  and 
(c)  Gases, 

and  all  three  have  a  commercial  value.  They  are  each  dealt 
with  in  the  next  chapter. 

Blast  furnaces  were  formerly  small,  and  were  built  of  heavy 
masonry,  with  a  lining  of  fireclay  blocks ;  now  they  are  tall 
and  comparatively  slender  in  appearance.  Formerly  the 
throats  were  open  and  gases  were  allowed  to  burn  at  the  top. 

Structurally,  the  modern  blast  furnace  is  a  tall  upright 
cylinder,  -sheathed  in  iron  or  mild  steel  plates,  and  having  a 
working  lining  of  good  firebricks.  The  blast  furnaces  in  a 
work  are  built  in  a  row,  each  being  as  close  to  the  others  -as 
convenient.  Fig.  8 1  shows  one  of  the  ranges  of  blast  furnaces 
at  Messrs.  Bell  Brothers'  works,  Port  Clarence,  Middlesbrough. 

Near  to  the  furnaces  are  grouped   the  arrangements  for 


190  IRON   AND   STEEL   MANUFACTURE. 

hoisting  the  raw  materials ;  the  blowing  engines  for  forcing, 
and  the  stoves  for  heating,*  the  air  blast ;  pipes  for  conveying 
the  exit  gases ;  accommodation  for  the  slag  bogies  or  cars,  and 
space  for  casting,  or  machinery  for  conveying,  the  pig  iron 
which  is  produced. 

Details  of  Structure. — The  foundations  for  a  large  erection 
for  dealing  with  heavy  materials  must  be  good.  Firm  land 
which  can  be  easily  drained  must  be  selected,  or  expense  will 
be  entailed  in  providing  and  driving  in  piles  and  making 
the  ground  suitable.  Extensive  concrete  foundations  may  be 
put  in.  The  firestones,  blocks,  or  bricks  which  constitute  the 
base  of  the  inner  part  of  the  furnace  must  be  designed  and 
laid  in  such  a  manner  as  to  resist  any  tendency  to  be  pushed 
directly  upwards  if  the  "  metal "  should  unfortunately  find  a 
way  underneath.  They  are  generally  set  so  as  to  form  a 
shallow  cavity,  or  an  inverted  arch,  and  are  so  placed  that 
pressure  from  beneath  forces  them  more  tightly  together. 

The  main  body  of  the  blast  furnace  is  carried  on  cast-iron 
hollow  columns  surmounted  by  a  lintel  of  heavy  cast-iron  or 
steel  plates.  Not  only  does  the  lintel  carry  the  brickwork,  but 
it  also  directly  supports  the  casing  of  rivetted  metal  plates. 
These  latter  sustain  the  weight  of  the  platform  at  the  top, 
over  which  the  charges  for  the  furnace  are  wheeled  in  barrows. 

Internally  the  furnace  consists  of  the  hearth,  or  well,  of 
brickwork  at  the  bottom,  which  is  built  up  from  the  founda- 
tion to  where  it  joins  the  brickwork  of  the  next  part — the 
bosh,  or  working  part.  Above  the  bosh  is  the  stack,  or  heat- 
intercepting  part. 

Viewed  from  the  top  the  stack  expands  in  diameter.  The 
widening  of  the  diameter  makes  allowance  for  the  expansion 
(due  to  heat)  of  the  materials  which  are  charged  in  from 
the  top  of  the  furnace,  and  permits  the  "  unpacking  "  of  the 
materials  as  they  descend.  The  bosh  contracts  in  diameter, 
so  that  the  materials  which  have  gone  down  so  far  may  be 
held  up  until  the  fuel  is  burned  away  at  or  near  the  top  of  the 
well,  and  the  then  melted  pig  iron  and  slag  gradually  drop 
into  the  hearth,  or  well,  where,  by  reason  of  difference  of 
density,  the  slag  and  pig  iron  separate  from  each  other,  and 

*  If  the  air  supplied  is  heated  before  it  is  forced  into  the  furnace  a 
large  saving  of  fuel  is  effected. 


Fig.  82. — Modern  Iron-smelting  Blast  Furnace.* 


A,  Cylinder  with 
plunger. 
B,  Beam. 
C,  Cone. 
D,  Cup. 
E,  Uptake. 
F,  Outlet  for  gases. 

G,  Downtake  or  down- 
comer. 
H,  Firebrick  lining. 
J,  Iron  plates. 
K,  Firebrick  lining. 
L,  Dust-catcher. 
M,  Downtake  from 
dust-catcher. 

N,  Iron  plates  for 
shell. 
0,  Lintel. 
P,  Iron  columns. 
Q,  Horse-shoe  main. 
R,  Goose  neck. 
S,  Tuyere. 

*  Details  from  The  Designing  and  Equipment  oj  Blast  Furnaces,  by 
John  L.  Stevenson. 


192  IRON    AND    STEEL    MANUFACTURE. 

are  in  due  course  each  tapped  out,  in  the  fluid  condition,  from 
the  furnace. 

The  inner  lining  of  the  furnace  is  of  good  firebricks  or 
blocks.  Bricks  are  now  preferred  to  the  large  blocks  which 
were  formerly  favoured  for  furnace-building.  True,  they  need 
more  setting  and  cementing,  but  bricks  are  more  likely  to  be 
thoroughly  kiln-fired.  Large  blocks  may  be  raw  in  the  heart, 
and  cause  trouble  when  the  furnace  becomes  hot  in  course  of 
a  campaign.  Bricks  of  secondary  quality  are  used  to  back  the 
bricks  which  constitute  the  lining.  A  space  of  1  inch  or  more 
is  left  between  the  bricks  and  the  metal  sheathing,  so  that  the 
structure  may  not  be  distorted  when  the  brickwork  gives  way 
slightly  after  starting  the  working  of  the  furnace.  The  inter- 
space may  be  partially  filled  with  granulated  slag. 

The  "Cup  and  Cone"  is  an  arrangement  for  charging  the 
solids  and  distributing  the  charge  in  the  furnace  in  the 
manner  best  suited  to  the  working  conditions.  The  arrange- 
ment keeps  the  throat  of  the  furnace  closed,  except  at  the 
instant*  of  charging  in  the  materials,  thus  enabling  most  of  the 
blast-furnace  gases  to  be  collected.  The  "cup"  consists  of 
iron  castings,  which,  when  bolted  together  and  fixed  in  posi- 
tion, complete  a  structure  which  is  like  the  wider  part  of  an 
inverted  hollow  cone.  The  "  cone "  is  also  of  iron  castings 
bolted  together  and  finished  to  fit  the  lower  edge  of  the  cup. 
It  is  suspended  to  one  arm  of  a  counterpoised  beam.  The 
charge  of  solid  materials  is  tipped  from  barrows  into  the 
circular,  tapered  trough  formed  by  the  cup  and  cone.  When 
the  beam  is  released  the  cone  *  descends,  and  the  materials 
slip  into  the  furnace.  The  cone  immediately  rises,  by  the 
weight  of  the  counterpoise  at  the  farther  end  of  the  beam,  and 
closes  the  "  mouth  "  or  "  throat "  of  the  furnace. 

In  order  to  avoid  the  jerking  which  would  arise  from  the 
sudden  lowering  and  raising  of  the  cone,  a  water  cylinder  with 
a  plunger  and  a  curved  connecting  pipe  is  provided.  A  rod 
from  the  plunger  within  the  cylinder  is  fastened  to  the 
weighted  end  of  the  beam.  On  being  released,  the  beam  end 
cannot  travel  faster  than  permitted  by  the  flow  of  water  from 
the  upper-  exit  of  the  cylinder  through  the  connecting  pipe 
(see  top  left  part  of  fig.  82)  to  the  lower  part  of  the  cylinder, 
*  Generally  called  the  "  bell"  by  blast-furnace  men. 


THE   BLAST   FURNACE    AND    ITS   EQUIPMENT.  193 

under  the  plunger.  And  when  the  cone  begins  to  rise  the 
beam  cannot  move  faster  than  allowed  by  the  checked  flow  of 
water  up  the  connecting  pipe  to  the  top  part  of  the  cylinder — 
above  the  plunger.  The  plunger  cannot  but  move  slowly  and 
smoothly.  The  water  acts  as  a  cushion,  and  a  moderated  and 
steady  lowering  and  raising  of  the  "  bell "  is  insured. 

The  diameter  and  the  angle  of  the  cone  have  a  marked 
effect  on  the  working  of  the  furnace  to  which  it  is  fitted.  It 
is  most  important  that  it  should  be  correctly  designed,  so  as  to 
cause  the  charge  to  be  spread  in  the  furnace  without  the 
lumpy  portions  of  the  charge  accumulating  either  in  the 
centre  or  towards  the  lining  of  the  furnace.  A  blast  furnace 
will  not  work  smoothly  unless  the  lumps  are  fairly  well  mixed 
among  the  "  smalls."  If  the  cone  is  not  wide  enough,  there 
will  be  an  accumulation  of  finer  ore  in  the  centre  and  of  lumps 
towards  the  sides  of  the  furnace ;  if  it  is  too  wide,  lumps  will 
gather  in  the  centre.  In  either  case,  the  ascending  gases, 
which  carry  on  much  of  the  furnace  work,  will  find  easy 
passage  between  the  lumps ;  and  where  the  smalls  are  close 
together  there  will  be  comparative  stagnation  and  a  tendency 
to  furnace  derangement.  Hence  the  great  importance  of  a  cup 
and  cone  properly  proportioned  to  the  furnace  and  the  ores, 
&c.,  so  that  the  lumps  and  the  smalls  will  be  well  mixed 
through  each  other  when  charged. 

The  air  required  to  urge  the  fire  within  the  furnace  is  forced 
in  through  tuyeres  which  are,  at  regular  intervals,  let  into  the 
furnace  at  an  uniform  level  above  the  hearth.  The  work  of 
the  furnace  is  carried  on  by  the  fuel  and  the  products  of  com- 
bustion. As  the  latter  ascend  they  meet  with,  and  impart 
heat  to,  the  descending  solids.  At  the  top,  the  gases  are  led 
off  from  the  furnace  through  an  outlet,  or  outlets,  into  the 
downcomer,  and  from  thence  into  the  culverts,  which  convey 
them  for  further  use. 

The  air  supply  is  forced  by  powerful  blowing  engines 
through  the  stoves  in  which  the  air  is  heated.*  The  hot  air 
from  the  hot-blast  stoves  is  conveyed  through  a  large  brick- 
lined  iron  pipe  known  as  the  hot-blast  main.  A  short  brick- 

*  Hot  air  is  used  in  all  iron-smelting  blast  furnaces  except  thoa» 
producing  cold-blast  pig  iron. 

13 


194  IRON    AND   STEEL    MANUFACTURE. 

lined  pipe  connects  the  hot-blast  main  with  the  horse-shoe 
main.  The  horse-shoe  main  is  a  large  brick-lined  iron  pipe 
which  almost  entirely  encircles  the  furnace.  It  is  carried 
on  brackets  which  are  bolted  to  the  cast-iron  columns  at  a 
suitable  height.  Pipes  called  goose-necks  descend  at  regular 
intervals,  and  conduct  the  air  supply  from  the  horse-shoe  main 
to  the  tuyeres  through  which  the  air  is  directly  forced  into 
the  furnace. 

As  the  hot-blast  tuyeres  (which  are  not  brick  lined  like  the 
horse-shoe  main,  nor  exposed  to  the  air  as  are  the  goose-necks) 
are  constantly  subjected  to  the  heat  of  the  furnace,  means 


Fig.  83.— Scotch  Tuyere. 

must  be  taken  to  prevent  the  melting  of  the  iron  of  which 
they  are  made,  and  no  better  method  is  known  and  practised 
than  that  devised  by  Mr.  Condie,  a  West  of  Scotland  blast- 
furnace manager,  shortly  after  the  hot  blast  was  introduced  by 
James  Beaumont  Neilson.  Condie's  tuyere — known  as  the 
Scotch  tuyere — consists  of  a  wrought-iron  pipe,  generally 
about  1  inch  diameter,  formed  into  a  tapering  coil  around 


Fig.  84. — Staffordshire  Tuyere.        Fig.  85. — Lloyd's  Spray  Tuyere. 

which  melted  pig  iron  has  been  moulded  to  the  shape  shown 
in  section  in  fig.  83.  When  the  tuyere  is  in  position  a  plentiful 
supply  of  water  is  caused  to  flow  through  the  coiled  pipe.  The 
water  carries  off  heat  so  quickly  that  the  iron  pipe  cannot  melt. 
Other  forms  of  tuyeres  are  the  Staffordshire  tuyere  (fig.  84) 
and  Lloyd's  spray  tuyere  (fig.  85). 


THE    BLAST    FURNACE    AND    ITS    EQUIPMENT.  195 

In  Foster's  Patent  Tuyere  the  water  is  drawn  through  the 
cooling  coil.  This  new  method  possesses  distinct  advantages. 

In  furnaces  designed  for  a  very  large  output  the  tuyeres 
are  made  of  bronze  or  of  pure  copper,  and  are  surrounded 
by  a  larger  bronze  " block  tuyere"  or  "Jumbo."  The  water 
blocks  now  so  extensively  used  outside  blast-furnace  boshes 
are  often  made  of  bronze. 

Dimensions  and  Output. — An  improved  blast  furnace  be- 
longing to  Dud  Dudley  (17th  century)  produced  7  tons  of  pig 
iron  in  one  week.  The  output  was  deemed  so  excessive  that 
a  riot  ensued,  and  the  new  blowing  arrangements  were 
destroyed  !  A  fully-equipped  American  blast  furnace  working 
on  easily  reduced  ores  has  produced  on  an  average  500  tons 
of  pig  iron  per  day.  The  present  output  is  about  430  tons 
per  day. 

A  modern  blast  furnace  of  average  capacity  may  be  of  the 
following  dimensions : — 


Height  of  furnace,  . 

Diameter  at  throat, 

,,          top  of  bosh, 
,,          top  of  hearth, 

Number  of  tuyeres, 
Diameter  of  tuyeres, 

Pressure  of  blast,    . 
Temperature  of  blast, 


80  feet. 
14    „ 
21     „ 
12    „ 

8  to  16. 

up  to  6  inches. 

10  Ibs.  per  square  inch. 
1,400°  F. 


For  regular  working  the  angle  or  slope  of  the  bosh  should 
be  about  75°.  Rapid  working  depends  on  the  design  of  the 
furnace,  the  blast  supply,  the  nature  of  the  burden,  and  other 
points. 

Furnaces  of  large  capacity  work  economically.  A  tall 
furnace  does  not  require  so  much  coke  for  the  reduction  of 
ore  as  a  shorter  furnace  does.  But  the  height  of  a  furnace 
is  limited  by  the  frailty  of  the  fuel — which  is  more  easily 
crushed  than  the  other  components  of  the  charge.  The 
mechanical  condition  of  the  ore  is  also  an  important  factor. 
There  is  at  the  present  time  a  tendency  to  abandon  furnaces 
of  100  feet  in  height  in  favour  of  90  or  80  feet  furnaces. 
The  diameter  of  a  blast  furnace  must  not  be  too  great,  or  the 
air  blast  will  not  be  able  to  get  near  enough  to  the  centre. 


196  IRON    AND    STEEL   MANUFACTURE. 

Blowing  engines  consist  essentially  of  large  cylinders  with 
clack  valves  which  respond  to  the  movement  of  the  piston 
within — opening  to  admit  air  while  the  piston  moves  in  one 
direction,  and  closing  when  it  moves  in  the  opposite  direction. 
The  air  piston  is  worked  from  a  steam  engine,  or,  as  in 
many  new  installations,  a  gas  engine.  Air  which  enters  the 
cylinder  is  forced  into  the  cold-blast  main,  which  conducts 
it  under  pressure  either  to  the  hot-blast  stove,  or  directly  to 
the  blast  furnace. 

The  Stoves  for  preheating  the  air  for  use  in  the  blast  furnace 
were  originally  like  boilers  and  chests  :  they  were  made  of 
malleable  iron  plates,  and  afterwards  of  cast  iron.  These 
remained  in  use  till  the  introduction  of  cast-iron  pipe  stoves, 
which  are  still  employed  in  some  works.  By  means  of  pipe 
stoves  air  can  be  heated  to  a  temperature  of  1,000°  P.,*  and 
maintained  steadily  at  a  temperature  of  about  800°  F.,  at 
which  the  limit  of  endurance  of  cast  iron  is  reached.  There 
is  also  a  danger  of  much  leakage  at  the  joints  or  sockets.  A 
great  saving  of  fuel  and  a  larger  output  of  pig  iron  accom- 
panied each  increase  of  temperature  arising  from  improvements 
in  the  construction  of  the  stoves. 

Firebrick  hot-blast  stoves  worked  on  the  regenerative  system 
satisfactorily  heat  the  blast  to  1,400°  F.,  and  even  up  to  1,500° 
F.,  and  enable  a  still  further  saving  of  fuel  to  be  effected,  and 
the  pig  iron  output  to  be  further  increased. 

Hot-blast  Pipe  Stoves  are  oblong  chambers  of  brickwork 
enclosing  a  range  of  cast-iron  pipes,  and  they  may  be  heated 
either  by  a  coal  fire,  or  by  gas  from  the  blast  furnaces.  Two 
pipes,  with  several  sockets  cast  on  at  equal  distances  apart,  are 
laid  horizontally  along  the  chamber.  Arched  pipes  are 
arranged,  each  extending  from  one  of  these  horizontal  pipes  to 
the  other,  and  having  their  ends  carefully  cemented  in  a  socket 
of  each.  Stops  are  placed  at  intervals  in  the  horizontal  pipes, 
so  as  to  cause  the  air,  which  is  forced  in  at  one  end,  to  travel 
successively  from  the  first  horizontal  pipe  to  the  others  many 
times.  As  the  air  travels  through  the  pipes  it  becomes  highly 
heated  and  expanded. 

*  Many  iron-masters  believed  that  when  the  air  was  heated  above 
600°  F.  they  were  on  dangerous  ground. 


THE    BLAST   FURNACE    AND    ITS    EQUIPMENT. 


197 


There  are  several  modifications  in  the  design  of  such  stoves. 
In  the  pistol  pipe  stove  the  upright  pipes  are  curved  over  at 
the  top,  and  an  internal  division  extends  nearly  to  the  end  of 
the  curved  part,  and  causes  the  air  to  travel  up  and  down  the 
same  pipe.  This  arrangement  reduces  by  half  the  number  of 
sockets.  In  the  Swedish  stove  all  the  pipes  are  laid  horizon- 
tally, and  the  bends  which  unite  them  are  jointed  outside  the 
stove.  Leakage  at  the  joints  can  thus  be  detected  at  once, 
and  if  a  pipe  is  supposed  to  be  cracked  the  jointings  can  be 
undone,  the  pipe  taken  out  and  examined,  and,  if  necessary, 
renewed  without  much  trouble. 


A,  Chimney. 

B,  Arched  pipe. 

C,  Brickwork. 

D,  Socket  for  pipe. 

E,  Horizontal  pipe. 

F,  Grate. 


Fig.  86.  —Cast-iron  Hot-blast  Stove. 

The  first  firebrick  hot-blast  stove  was  designed  by  the  late 
Mr.  Edward  A.  Cowper.  Such  stoves  are  heated  by  blast- 
furnace, gas,  and  worked  on  the  regenerative  system  as  applied 
in  the  Siemens  furnace.  A  Cowper  stove  (like  others  of 
modern  design)  is  externally  a  tall,  upright,  cylindrical  shell, 
with  dome-shaped  roof,  of  mild-steel  plates.  The  plates  are 
firmly  rivetted  together  so  as  to  form  a  gas-tight  structure, 
and  a  lining  of  firebrick  is  built  within  to  protect  the  plates. 
A  firebrick  .flame-flue  or  combustion  chamber  of  elliptical 
section,  and  approaching  to  the  full  height  of  the  stove,  is 
constructed.  Divisions  are  arranged  at  the  lower  part  of  the 


198 


IRON    AND    STEEL    MANUFACTURE. 


chamber  to  split  the  gas  into  sheets,  so  that  speedy  and  com- 
plete combustion  is  effected  with  little  excess  of  air.  Cowper's 
stove  is  sketched  in  figs.  87  and  88 — the  latter  being  on  a 
scale  double  that  of  the  former. 


A,  Culvert  for  gases  from 

blast  furnaces. 

B,  Blast-furnace     gas 

valve. 

C,  Air  inlet. 

D,  Divisions. 

E,  Combustion     chamber 

or  flame-flue. 

F,  Outlet  for  hot  blast. 

G,  Hot-blast  valve. 

H,  Iron     or     mild -steel 

plates. 

I,  Firebrick  lining. 
J,  Combustion     chamber 

or  flame-flue. 
L,  Manhole. 
M,  Regenerative  brick. 
N,  Grids. 
0,  Columns. 
P,  Chimney  valve. 
R,  Culvert  to  chimney. 


Fig.  87.— Cowper's  Hot-blast  Stove. 

The  remainder  of  the  interior  is  filled  in  with  firebricks,  so 
designed  and  laid  as  to  form  a  number  of  hexagonal  (six-sided) 
passages,  each  extending  from  iron  grids  near  the  bottom  of 
the  stove  up  to  the  level  of  the  top  of  the  combustion  chamber. 
The  bricks  which  make  up  the  "honeycomb  filling"  leave 
passages  of  about  6  or  7  inches  wide,  separated  from  each 


THE    BLAST    FURNACE    AND    ITS    EQUIPMENT. 


199 


other  by  walls  2  inches  thick.  To  minimise  lodgment  of  dust 
carried  over  in  the  blast-furnace  gas,  the  inner  corners  are 
slightly  rounded  and  the  topmost  bricks  are  tapered.  The 
grids  are  carried  on  girders  supported  on  short  iron  columns. 
There  are  cleaning  doors  near  the  top  and  manholes  near  the 
bottom,  as  well  as  one  at  the  top  of  the  dome.  The  stove  is 


Fig.  88.— Plan  of  Cowper's  Hot-blast  Stove. 


A,  Hot-blast  pipe. 

B,  Hot-blast  valve. 

C,  Combustion  chamber  or  flame- 

flue. 

D,  Regenerator  (hexagon)  bricks. 

E,  Inner  firebrick  lining. 

F,  Cold  air  inlet. 

G,  Chimney  valve. 


H,  Iron  or  mild-steel  plates. 

J,  Firebrick  lining. 

K,  Columns  and  supports  for  grids. 

L,  Opening  to  regenerators. 

N,  Grids  for  supporting  regenera- 
tor bricks. 

0,  Brickwork  lining  for  flame-flue 
chamber. 


set  on  a  substantial  foundation,  and  flues  are  arranged  under- 
ground for  the  conveyance  of  the  blast-furnace  gas,  and  for 
taking  off  the  spent  gases  to  the  chimney.  Gas,  air,  and 
chimney  valves  are  provided,  and  will  be  better  understood  by 
an  examination  of  the  sketches. 


200  IRON    AND    STEEL    MANUFACTURE. 

Other  forms  of  firebrick  stoves  are  : — 

The   Whitwell, 
The   Massick  &   Crookes, 
The   Ford    &   Moncur,  and 
The  Cowper-Kennedy. 

They  are  all  worked  on  the  same  principle  as  the  Cowper 
stove. 

Working  the  Hot-blast  Stoves. — Blast-furnace  gas  *  is 
admitted  to  the  combustion  chamber  through  the  gas  valve. 
At  the  same  time  air  is  admitted  through  the  adjoining  air 
valve.  The  combustion  chamber  being  hot,  ignition  takes 
place  and  a  long  tongue  of  flame  shoots  up  the  combustion 
chamber.  The  hot  products  of  combustion  travel  up  the 
flame-flue  and  down  through  the  hexagonal  passages,  impart- 
ing much  heat  to  the  brickwork  before  being  drawn  off 
through  the  chimney  valve  to  the  tall  stack  by  which  they 
escape  into  the  atmosphere.  When  the  bricks  have  thus  been 
heated  sufficiently,  the  supply  of  gas  and  air  is  turned  off  and 
the  chimney  valve  is  closed.  Air,  forced  in  by  the  blowing 
engine,  is  now  sent  through  the  cold-blast  valve  into  the 
stove,  and  the  air  becoming  heated  by  contact  with  the  hot 
brickwork  while  travelling  up  the  passages  and  down  the 
combustion  chamber,  emerges  through  the  hot-blast  valve  (at 
a  temperature  of  1,500°  F.  to  1,100°  F.)  to  the  blast  furnace. 
When  the  stove  has  cooled  down  to  the  lower  temperature 
the  open  valves  are  closed  and  the  closed  ones  opened  for  the 
entrance  of  blast-furnace  gas  and  air  for  reheating.  Air  is 
forced  through  the  neighbouring  stove,  which  has  been  highly 
heated  in  the  interval.  The  stoves  are  worked  in  pairs  or 
double  pairs,  or  in  sets  of  three. 

The  current  of  gas  from  the  blast  furnace  unavoidably 
carries  in  dust  which  impairs  the  efficiency  of  the  stove  by 
covering  the  regenerative  brickwork  with  a  coating  which 
does  not  readily  transmit  heat.  As  a  consequence  each  stove 
requires  to  be  cleaned  at  intervals,  or  arrangements  are  made 
for  driving  out  the  dust  by  the  blast  at  each  change  of 
the  stove. 

*  See  composition  on  p.  221- 


THE    BLAST    FURNACE   AND    ITS    EQUIPMENT.  201 

The  hoists  or  lifts  by  which  materials  are  hoisted  to  the 
top  of  the  blast  furnace  may  he  either  vertical  or  sloping,  and 
they  may  be  worked  by  means  of  a  winding  engine  driven 
by  steam,  by  pneumatic  or  by  hydraulic  pressure,  or  by  a 
water  balance.  The  newest  and  best  method  is  by  means  of 
electricity. 

For  the  vertical  hoist  with  direct  winding,  a  tower  is  built 
with  its  top  higher  than  the  charging  platform  at  the  top  of 
the  furnace.  A  wheel  and  axle  surmounts  the  tower,  and 
over  the  wheel  a  rope  passes,  which  is  fastened  at  one  end  to 
the  movable  platform  or  cage,  while  the  other  is  attached  to  a 
drum  in  the  engine-house.  When  the  drum  is  caused  to 
revolve,  the  rope  is  coiled  round  it,  and  the  movable  platform 
or  lift,  with  its  laden  barrows,  is  raised.  On  reversing  the 
direction  of  the  revolving  drum,  the  moving  platform,  with 
the  empty  barrows,  descends.  Hoisting  plant  may  be  dupli- 
cated, and  arranged  so  that  as  one  lift  is  raised  the  other 
descends.  In  fig.  81  hoists  are  shown.  In  this  instance  they 
are  lattice-work  structures  with  wheels  at  the  top. 

In  the  inclined  hoist  the  track  from  the  ground  level  to 
the  furnace  tops  generally  slopes  at  an  angle  which  is  largely 
determined  by  the  space  at  disposal.  The  movable  platform 
— which,  having  one  pair  of  wheels  larger  than  the  other, 
remains  level — is  pulled  up  by  means  of  cables. 

For  working  the  water-balance  lift,  water  is  steadily 
pumped  to  a  cistern  at  the  top  of  the  furnace.  Two  plat- 
forms are  worked  together.  Under  the  sole  of  each  platform 
there  is  a  tank.  Water  is  run  into  the  tank  of  the  movable 
platform  which  is  at  the  top,  in  quantity  more  than  sufficient 
to  counterbalance  the  weight  of  the  other  platform  and  its 
load.  On  being  released  the  water-laden  platform  descends 
and  the  other  one  is  raised.  The  water  is  then  run  out  of 
the  tank  of  the  platform  which  is  at  the  bottom.  At  the 
same  time  water  is  allowed  to  flow  into  the  tank  of  the 
platform  which  is  then  at  the  top. 

Within  recent  years  there  have  been  considerable  develop- 
ments in  the  equipment  of  blast  furnaces.  Water  for  cooling 
is  now  plentifully  supplied.  There  has  been  a  liberal  aug- 
mentation of  blowing  and  heating  power.  Charging  is  expe- 


202  IRON    AND    STEEL    MANUFACTURE. 

ditiously  performed  by  means  of  electrically-propelled  skips 
which  quickly  travel  on  aerial  rails  and  discharge  through 
a   rotating    distributor   into    the   furnace,    the   whole   being 
controlled  by  one  man  at  the  bottom.     Costly  machines  for 
"  casting  "  the  iron  into  pigs  as  it  comes  from  the  furnace,  or 
cranes  for  removing  the  pig  iron  from  the  sand  beds  and 
'  breaking  and  delivering  into  trucks,  have  also  been  provided. 
Some   modern  appliances  are  described  in  the  appendix 
to  this  volume. 


203 


CHAPTER    XXL 
THE   WORKING   OF   A  BLAST   FURNACE. 

THE  work  done  in  a  blast  furnace  is  the  extraction  of  iron 
from  ores  and  the  production  of  pig  iron,  which  is  the  crude, 
impure  form  in  which  iron  is  tapped  from  the  blast  furnace. 

As  delivered  at  the  blast  furnace  the  ore  contains  — 

(a)  Iron  and  manganese. 

(b)  Oxygen  in  chemical  union  with  these  metals. 

(c)  Earthy  impurities  (the  gangue)  associated  with  the 

metallic  oxides. 

(d)  Moisture,    which    is    soon    vaporised    in   the    blast 

furnace,  and  escapes  as  steam  in  the  exit  gases. 

It  need  not  be  more  than  mentioned,  at  this  point,  that  the 
ores  contain  the  iron  which  is  wanted,  that  the  fuel  supplies 
the  heat  and  the  chemical  energy  needed,  and  that  the  func- 
tion of  the  flux  is  to  form,  by  combining  with  the  gangue,  a 
slag  basic  enough  to  absorb  most  of  the  sulphur  of  the  fuel  and 
ore,  and  fluid  enough  to  flow  from  the  furnace  when  tapped. 

The  ore  and  the  flux  make  up  the  burden  of  the  furnace; 
the  ore,  flux,  and  fuel  make  up  the  charge.  This  statement 
may  be  expressed  thus  :  — 


Fuel. 

A  certain  number  of  charges  —  enough  to  fill  the  space  at 
the  cup  and  cone  —  make  up  a  round. 

The  smooth  working  of  a  furnace,  and  the  character  of  the 
pig  iron  produced,  depend  largely  on  the  relative  weight  and 
quality  of  the  burden  to  the  weight  and  quality  of  the  fuel. 
It  is  the  fuel  that  "  carries  "  the  burden.  If  the  ore  and  flux 


204  IRON    AND   STEEL   MANUFACTURE. 

together  are  heavy,  in  proportion  to  the  fuel,  the  furnace  is 
said  to  have  a  heavy  burden.  But  if,  on  the  other  hand,  the 
ore  and  flux  together  are  light,  in  proportion  to  the  fuel,  the 
furnace  is  said  to  have  a  light  burden.  By  increasing  the 
burden  on  a  furnace  the  output  may  be  increased,  while  less 
fuel  is  required  per  ton  of  pig  iron  produced. 

Fuel. — The  subject  of  fuel  is  dealt  with  in  Chapter  xxiii. 
But  it  may  be  noted  here  that  the  kind  of  fuel  used  in  the 
blast  furnaces  of  a  district  depends  on  the  local  supplies, 
or  on  the  price  at  which  fuel  from  another  district  can  be 
introduced. 

Coal  and  Coke. — Where  the  coal  is  suitable  for  coking  it 
is  coked,  but  if  it  is  not  of  a  coking  nature  it  is  used  in  the 
"  raw  "  state — that  is,  without  being  coked  before  charging. 
Coke  is  preferred  to  coal  for  blast-furnace  purposes.  It  yields 
a  more  intense  local  heat,  and  is  stronger  than  coal.  Blast 
furnaces  which  are  to  be  coke-fed  are  built  of  a  greater  height 
than  those  intended  to  be  coal-fed. 

Raw  Coal  is  used  in  Scotland  and  in  North  Staffordshire. 
In  some  South  Staffordshire  works  both  coal  and  coke  are 
charged ;  in  other  districts  in  Britain  coke  is  used  almost 
exclusively. 

Other  Fuels. — Charcoal,  which  is  the  purest  of  the  solid 
fuels,  is  much  used  in  Sweden,  because  in  that  country  coal 
is  not  plentiful,  and  wood — which  is  converted  into  charcoal 
by  a  process  like  coking — *  can  be  profitably  grown.  Lignite, 
or  brown  coal,  which  is  abundant  in  some  parts  of  Germany, 
is  used  in  some  blast  furnaces  there.  Anthracite  has  been 
employed  in  some  of  the  Welsh  blast  furnaces,  is  charged  in 
small  quantities  into  a  few  English  blast  furnaces,  and  is 
freely  used  in  some  American  ones.  It  requires  a  strong 
blast.  In  districts  in  process  of  being  cleared  for  civilisation 
wood  has  been  used  as  fuel.  The  use  of  dried  and  compressed 
peat  has  been  proposed. 

For  composition  of  fuels  see  p.  226. 

Flux. — For  the  purpose  of  providing  lime  to  act  as  a  flux 

*  Charcoal  was  prepared  long  before  coal  -was  coked.  The  earliest 
methods  of  making  coke  were  clearly  copied  from  the  practice  of 
charcoal  burning. 


THE    WORKING    OF    A    BLAST    FURNACE.  205 

for  the  silica  and  alumina  in  the  iron  ore,  &c.,  and  which  are 
infusible  at  the  blast-furnace  temperature,  limestone  forms 
part  of  most  blast-furnace  charges.  The  limestone  contains 
calcic  carbonate  (CaO,  C02)  and  is  soon  calcined  :  the  carbon 
dioxide  is  liberated  and  escapes  in  the  blast-furnace  gases. 
The  lime  (CaO)  which  is  left  enters  into  combination  with 
silica,  forming  calcic  silicate,  a  compound  the  melting  point 
of  which  is  below  the  temperature  of  the  blast  furnace.  Com- 
pound silicates  melt  still  more  easily,  as  explained  on  p.  229. 

Some  ores  are  self -going  or  self  -  fluxing ;  in  them  the 
proportions  of  silica  and  lime — which,  when  highly  heated, 
mutually  combine  with  each  other  to  form  a  compound  which 
becomes  fluid  at  a  high  temperature — are  (naturally)  so  pro- 
portioned that  addition  of  flux  is  unnecessary. 

By  judiciously  mixing  iron  ores  in  proper  proportions,  a 
self-fluxing  burden  may  be  charged  into  the  furnace.  A  good 
example  of  this  practice  is  seen  in  the  Fordingham  district, 
where  the  limey  iron  ores  of  North  Lincolnshire  are  mixed 
with  the  more  siliceous  iron  ores  of  Mid-Lincolnshire.  These 
ores  vary  very  widely  in  composition,  but  the  following  may 
be  taken  as  approximately  representing  the  percentage  of  the 
chief  components : — 


Chief  Constituents. 

Fordingham 

Mid- 
Lincolnshire 

Ore. 

Metallic  iron,*      ..... 

33 

39 

Metallic  manganese,* 

1-5 

1 

Silica  and  alumina,       .... 

11 

22 

19 

4 

It  is  customary  to  load  up  separately  the  ore  from  the 
various  well-marked  layers  of  the  quarry  or  mine,  and  to 
stock  each  in  a  separate  "  drop  "  at  the  blast  furnaces.  From 
these  the  ore  is  withdrawn  in  such  quantities  as  will  yield  a 
smooth-working  mixture,  thus  utilising  all  the  Fordingham 
ores  and  guarding  against  the  old  erratic  results. 

*  These  exist  in  the  ore  in  a  highly-oxidised  state. 


206  IRON    AND    STEEL    MANUFACTURE. 

In  making  up  a  blast-furnace  burden,  as  much  suitable  iron- 
bearing  material  as  possible  should  be  used  as  can  be  had  at 
a  reasonable  price. 

The  work  done  in  a  blast  furnace  includes — 

(a)  Reduction  of  the  iron  and  manganese  compounds  to  the 

metallic  state,  and 

(b)  Separation  of  the  iron  from  the  gangue. 

Incidentally,  the  iron  takes  up  carbon  (C)  from  the  fuel, 
and  silicon  (Si),  phosphorus  (P),  and  sulphur  (S),  which  have 
been  reduced  from  materials  in  the  charge.  The  compound 
of  iron  with  these  (and  sometimes  other)  elements  constitutes 
pig  iron.  The  term  "  cast  iron,"  which  is  sometimes  applied, 
is  confusing :  cast  iron  is  pig  iron  which  has  been  cast  into  a 
finished  shape. 

In  a  working  blast  furnace  there  are  steady  movements  of 
materials  in  opposite  directions.  The  solid  materials — the 
ore,  the  fuel,  and  the  flux — which  are  charged  in  at  the  top 
of  the  furnace,  descend  gradually.  These  are  met  by  an 
ascending  current  of  hot  reducing  gases  which  seek  their 
upward  way  between  the  pieces  of  descending  materials.  By 
tracing,  separately,  each  of  these  counter  currents,  an  under- 
standing of  the  working  may  be  arrived  at. 

The  Upward  Current. — The  air  for  the  blast  furnace  is 
forced  by  the  blowing  engines  along  the  cold-blast  main  to 
the  hot-blast  stoves,  where  it  is  heated.  From  the  stoves  the 
hot  air  is  sent  through  the  hot-blast  main,  horse-shoe  main, 
goose-necks,  and  tuyeres  into  the  furnace.  In  the  furnace 
the  hot  air  is  brought  into  contact  with  fuel  which  is  already 
glowing;  the  oxygen  of  the  air  enters  into  chemical  union 
with  the  combustible  elements  of  the  fuel  and  creates  a  very 
high  temperature.  The  chemical  action  of  oxygen  on  excess 
of  incandescent  fuel  produces  carbon  monoxide,  as  explained 
on  p.  209. 

Carbon  monoxide,  being  eager  for  more  oxygen,  takes  it 
from  those  descending  oxides  which  part  most  easily  with  it. 
This  transferring  of  oxygen  is  known  as  reduction,  and  the 
substance  which  parts  with  its  oxygen  is  said  to  be  reduced. 


THE    WORKING    OF   A    BLAST   FURNACE.  207 

Oxide  of  iron  is  readily  reduced  to  metallic  iron  by  the  action 
of  hot  carbon  monoxide  and  other  reducing  gases  in  the 
ascending  current.  The  up-going  gases  not  only  perform 
the  chemical  duty  of  reducing  the  ore,  but  they  impart  much 
heat  to  the  solids  which  are  on  their  way  down.  On  reaching 
the  top  of  the  furnace  the  gases  are  taken  off  through  one 
or  more  openings  into  the  downtake,  or  "downcomer,"  or 
"bustle  pipe,"  and  set  to  do  more  useful  work.  When  the 
gases  are  quite  spent  they  are  led  off  by  the  chimney  into 
the  air. 

The  Course  of  the  Solid  Materials  in  the  Blast  Furnace.— 
The  ore,  fuel,  and  flux  are  conveyed  by  barrows  to  a  weighing 
machine,  and  are  then  hoisted  to  the  platform  at  the  top 
of  the  furnace.  The  contents  of  the  barrows  are  tipped 
into  the  circular  hollow  formed  by  the  cup  and  cone.  The 
"  fillers,"  as  the  men  at  the  top  of  the  furnace  are  called, 
withdraw  to  a  safe  distance  and  lower  the  cone,  thereby 
charging  and  spreading  the  materials  in  the  furnace.  The 
cone  is  then  raised  into  position,  and  thus  the  mouth  of  the 
furnace  is  closed  and  the  further  escape  of  gases — which 
occurred  during  the  momentary  lowering  of  the  cone — is 
prevented. 

The  solids  are  soon  acted  on  by  the  hot  reducing  gases, 
but  it  is  not  until  the  hottest  zone  of  the  furnace  is  reached 
that  the  reduction  and  separation  are  completed. 

Provision  is  made  in  the  design  of  the  blast  furnace  for  the 
expansion  due  to  the  heating  of  the  descending  materials. 
When  a  certain  point  is  reached,  however,  a  diminution  occurs 
— fuel  is  burned  and  the  pig  iron  and  slag  become  molten 
and  drop  down  into  the  well  of  the  furnace.  There  the  pig 
iron  and  slag  separate  from  each  other  because  of  the  differ- 
ence of  density.  Slag,  being  lighter,  floats  on  the  top  of  the 
pig  iron  and  is  tapped  off  as  often  as  required.  The  pig  iron 
is  tapped  from  the  furnace  every  twelve,  eight,  or  six  hours, 
and  even  more  frequently  in  some  instances. 

The  pig  iron  as  it  is  tapped  from  the  furnace  may  be 
allowed  to  flow  into  the  recesses  previously  moulded  in  sand 
in  the  slightly  sloping  terrace  in  front  of  the  blast  furnace, 
which  is  known  as  the  "  pig  bed."  The  pig  iron  flows  down 


208 


IRON    AND   STEEL    MANUFACTURE. 


the  runner — which  is  a  channel  in  the  sand  traversing  nearly 
the  entire  length  of  the  pig  bed — into  the  moulded  cross 
channels  which  are  known  as  the  "  sows,"  and  from  the  sows 
into  the  "  pig  "  moulds  which  are  again  at  right  angles. 

Each  "  pig  "  is  about  a  yard  long  and  weighs  over  1  cwt. 

As  the  molten  pig  iron  comes  from  the  furnace  it  is 
allowed  to  flow  to  the  end  of  the  runner  and  along  the  lowest 


sow"  into  the  connected 


"  pig  "  moulds. 


\AThen  these  are 


Fig.  89. — Pig  Beds  in  front  of  Blast  Furnace. 

filled  with  fluid  pig  iron  the  runner  is  blocked  below  the  next 
sow  and  a  way  is  made  for  the  metal  to  flow  along  the  sow 
into  the  next  row  of  pigs.  Thus,  one  by  one  the  rows  receive 
the  pig  iron  until  the  "  cast "  is  finished ;  that  is,  until  all  the 
iron  obtainable  at  that  time  from  the  hearth  has  run  out 
(fig.  89),  Steps  may  be  taken  to  hasten  the  cooling  of  the 
pigs,  which,  when  sufficiently  solidified,  are  broken  off  from 
the  sows,  and  the  sows  from  the  runners.  These  are  broken 


THE  WORKING  OF  A  BLAST  FURNACE.          209 

into  useful  sizes.  In  due  course  all  the  pig  iron  is  lifted  and 
conveyed  to  trucks. 

In  some  other  countries  it  is  customary  to  "  cast "  the  pig 
iron  under  cover. 

From  a  mechanical  point  of  view,  sand  is  a  suitable  sub- 
stance in  which  to  cast  pig  iron ;  from  a  chemical  standpoint, 
it  is  one  of  the  worst  materials  known.  Various  other 
substances  have  been  suggested  and  some  have  been  tried, 
such  as  coke  dust  and  fine  ore.  In  Sweden,  heavy  cast-iron 
troughs  or  trays  are  extensively  used  as  moulds  for  pig  iron, 
with  good  results. 

In  a  blast  furnace  which  is  making  pig  iron,  all,  or  nearly 
all,  the  iron  is  reduced ;  the  proportion  of  manganese  and  of 
silicon  reduced  will  depend  on  the  conditions  prevailing  in  the 
furnace,  and  the  conditions  will  decidedly  influence  the  amount 
of  carbon  and  sulphur  in  the  pig  iron  produced.  With  very 
few  exceptions  nearly  all  the  phosphorus  compounds  in  the  ore, 
fuel,  and  flux  are  decomposed,  all  but  a  little  of  the  phosphorus 
going  into  the  pig  iron. 

Of  the  descending  materials  m  a  working  blast  furnace  all  that 
retain  their  oxygen  go  into  the  slag,  and  (with  the  exception  of  some 
sulphur  which  is  collected  in  the  slag)  all  that  are  reduced  go  into 
the  pig  iron. 

The  chemical  work  of  a  blast   furnace  is  effected    by  a 

strongly  reducing  action. 

The  chemical  reactions  which  take  place  are : — 

Carbon,  when   burned  in  a  blast  furnace,   forms    carbon 

monoxide  (CO).    This  is  believed  to  be  effected  in  two  stages. 

Firstly,  carbon  dioxide  (CO,,)  is  formed — 

C  +         02  C02 

Carbon      and      oxygen     yield     carbon  dioxide 

and  then  the  dioxide  is  converted  by  the  excess  of  glowing 
carbon  into  carbon  monoxide,  thus — 

CO2  +         C  2CO 

Carbon  dioxide    and    carbon    yield    carbon  monoxide. 

In  the  course  of  his  extensive  investigations  on  blast-furnace 
eases  the  author  has  been  unable  to  find  carbon  dioxide  in  the 

14 


210  IRON    AND    STEEL    MANUFACTUEE. 

gases  drawn  off  from  the  hearth.  But  whether  carbon  dioxide 
is  formed  in  the  first  instance,  or  the  monoxide  is  formed 
directly,  there  can  be  no  difference  in  the  chemical  or  the 
thermal  effects. 

Although  there  is  reason  to  believe  that  the  cyanides  which 
are  present  in  the  gases  in  the  lower  regions  of  the  blast 
furnace  exert  influence  in  carrying  on  reduction,  and  that 
hydrogen  must  have  a  notable  effect,  the  chief  agent  in 
carrying  on  reduction  must  be  either  hot  carbon  or  carbon 
monoxide,  both  of  which  are  present  in  large  quantities.  The 
action  of  the  latter  may  be  represented  by  the  following 
chemical  equations  : — 

Reduction  of  ferric  oxide — 

+  SCO  =  2Fe  +         3C02 

and  -f    carbon    \  vield          iron         and  I  c?rbon 
[  monoxide  f  y  (  dioxide. 

Reduction  of  manganese  oxide — 

Mn3O4  +  4CO  =  3Mn  +         4C02 

Manganese  oxide   and  |  J^^l  Vidd 


Reduction  of  phosphorus  pentoxide  (often  called  phosphoric 
acid)  — 

P205  +  SCO  2P  +         5C02 


Phosphoric  acid    and  h      ***    P^orus   ^  { 


Reduction  of  ferric  oxide  takes  place  in  the  upper  region  of 
the  stack,  but  is  not  completed  till  the  still  unreduced  portions 
of  the  ore  reach  the  bosh. 

The  composition  of  the  gases  from  charcoal-fed  and  coke-fed 
blast  furnaces  proves  that  oxidation  of  carbon  or  carbon 
monoxide  to  carbon  dioxide  takes  place. 

Carbon  Impregnation.  —  Hot  iron  can  decompose  carbon 

monoxide,  thus  — 

2CO  =  C  +  C02. 

The  carbon  so  liberated  enters  into  combination  with,  or 
deposits  carbon  on,  the  spongy  pig  iron. 

It  has  been  experimentally  proved  that,  on  a  small  scale, 


THE    WORKING    OF    A    BLAST    FURNACE.  211 

carbon  monoxide  cannot  reduce  silica.  We  may  therefore 
represent  it  as  being  directly  reduced  by  carbon,  thus — 

Si02       +          2C  Si          +  2CO 

Silica     and    carbon    yield     silicon    and    carbon  •tuon.n.rlde. 

It  is  not  safe,  however,  to  assume  that  reactions  on  the 
small  scale  are  the  same  as  those  which  take  place  on  a 
large  scale. 

In  the  formation  of  slags  chemical  union  takes  place 
between  the  lime  of  the  flux  and  some  of  the  silica  of  the 
ore  or  the  ash  of  the  fuel,  and  the  reaction  may  be  represented 
thus — 

2CaO        +         Si02          =  2CaO  .  Si02 

Lime      and      silica      yield      silicate  of  lime. 

Any  free  alumina  which  may  be  present  would  also  combine 
with  silica,  and  the  reaction  may  be  stated  thus — 

2A1203          +        3Si02        =  2A1203 .  3Si02 

Alumina      and      silica      yield      silicate  of  alumina. 

The  silicates  of  lime  and  alumina  unite  to  form  a  compound 
silicate.  Some  blast-furnace  slags  have  a  composition  which 
can  be  summed  in  the  formula — 

2A1203,  3Si02     +     6(2CaO,  Si02). 
Calculation  shows  such  a  slag  to  consist  of — 

Silica       (Si02),          .          .          3 8"  14  per  cent. 
Alumina  (AlgOj),       .         .         14-41 
Lime        (CaO),         .          .         47'45       „ 

Other  oxides  are  present  in  the  slags,  notably  oxide  of  man- 
ganese (MnO)  and  magnesic  oxide  or  magnesia  (MgO).  These 
replace,  as  far  as  they  can,  the  lime :  being  bases  they  can 
combine  with  silica.  Very  rarely  blast-furnace  slags  are 
produced  which  contain  no  lime. 

When  a  furnace  is  working  on  a  light  burden  the  slag 
produced  is  generally  white  or  grey;  when  the  burden  is 
heavy  a  dark  coloured  or  black  slag  is  usually  produced. 
Such  dark  or  black  slags  contain  ferrous  oxide  (FeO)  which, 


212  IRON    AND    STEEL    MANUFACTURE. 

when  in  combination  with  silica,  forms  a  very  fluid  com- 
pound at  the  blast-furnace  temperature.  These  black,  ferrous, 
scouring  slags  are  very  severe  on  the  furnace  lining.  Slags 
containing  manganese  in  notable  amount  may  be  brown 
or  yellow  coloured.  Portions  which  contain  manganese  and 
much  silica  are  green  coloured.  If  much  lime  is  present  the 
slag  may  have  a  cold,  stony  appearance,  while  presence  of 
much  alumina  is  usually  shown  by  the  opalescent  character 
of  the  slag. 

Quickly-cooled  slags  are  glassy  and  present  a  shell-like 
(conchoidal)  fracture,  but  if  cooled  slowly  the  same  slag  may 
be  dull  in  appearance. 

Disposal  of  Blast-furnace  Slag. — The  slag  issues  from  the 
furnace  in  the  fluid  condition,  and  is  allowed  to  flow  into  iron 
tubs  or  ladles  which  are  set  on  trucks  or  trolleys.  It  may  be 
(a)  applied  to  useful  purpose,  or  (b)  be  tipped  on  heaps  and 
encumber  the  ground,  or  (c)  be  granulated  and  carried  away 
by  rivers,  or  (d)  be  conveyed  to  sea  on  barges  and  tipped  into 
deep  water. 

Of  late  years  a  considerable  quantity  of  blast-furnace  slag 
has  been  granulated  in  water  and  made  into  cement  or  bricks. 
Slag  wool  is  also  made,  and  large  quantities  of  slag  are  used 
for  road  making  and  mending  and  for  "  ballast "  between 
railway  sleepers.  In  some  iron-making  districts  the  whole  of 
the  slag  is  utilised. 

Slag  intended  to  be  tipped  on  heaps  may  either  be  allowed 
to  solidify  in  the  large  ladle  in  which  it  is  caught  and  the 
"  ball "  tipped  on  the  slag  hill,  or  as  soon  as  the  ladle  is  full 
it  may  be  taken  to  the  top  of  the  slag  hill  and  the  contents 
poured  out  there. 

On  the  European  continent  it  is  customary  in  some  works 
to  permit  the  slag  to  trickle  to  the  nearest  river.  Contact 
with  the  water  into  which  it  flows  has  the  immediate  effect 
of  breaking  it  up  into  grains,  and  these  are  carried  away  by 
the  current. 


213 


CHAPTER   XXII. 
THE   PRODUCTS   OP   THE   BLAST   FURNACE. 

THE  chief  aim  of  the  blast-furnace  manager  is  the  production 
of  good  pig  iron  at  the  lowest  possible  cost.  In  recent  times 
the  value  of  the  bye-products — gas  and  slag — have  received 
a  considerable  amount  of  attention. 

Pig  Iron. — The  purpose  for  which  a  lot  of  pig  iron  is  best 
suited,  and  the  price  it  will  command,  is  largely  determined 
by  the  percentage  of  phosphorus  which  it  contains.  It  has 
already  been  pointed  out  that,  with  few  exceptions,  almost  all 
the  phosphorus  in  the  blast-furnace  charge  goes  into  the  pig 
iron.  Hence,  it  follows,  that  in  order  to  regulate  the  amount 
of  that  element  in  the  pig  iron  which  is  to  be  produced,  the 
charge  must  be  carefully  selected.  If  pig  iron  with  a  small 
percentage  of  phosphorus  is  required,  care  must  be  taken  to 
exclude  ore,  fuel,  and  flux  which  contain  more  than  a  little  of 
that  element — for  unfortunately  none  of  these  are  quite  free 
from  phosphorus,  and  the  total  amount  may  irretrievably  injure 
the  quality  of  the  pig  iron.  On  the  other  hand,  some  classes 
of  pig  iron,  such  as  that  used  in  the  basic  Bessemer  process, 
must  contain  a  decided  amount  of  phosphorus,  and,  within  a 
limit  which  is  seldom  if  ever  exceeded,  more  phosphorus  is 
desirable.  In  'a  lesser,  but  essential,  degree  phosphorus  is 
necessary  in  foundry  pig  iron. 

The  following  may  be  taken  as  representating,  in  round 
numbers,  the  composition  of  certain  pig  irons  : — 


Constituents. 

Swedish. 

Bessemer. 

Foundry. 

Forge. 

Cleveland. 

Basic. 

Graphitic  carbon, 

2-00 

3-30 

2-75 

2-00 

3-20 

0-50 

Combined  carbon, 

2-00 

0-50 

0-75 

1-00 

0-50 

2-80 

Silicon, 

1  "20 

2-20 

2-00 

1-00 

2-60 

0-50 

Phosphorus,    .      0'03 

0-05 

0'90      1'30 

1-60 

3-00 

Sulphur, 

o-oi 

0-04 

0-09 

o-io 

0-08 

0-07 

Manganese, 

3-00 

0-50 

0-60 

0-50 

0-60 

2-00 

Iron,   . 

91-76 

93-41 

93-41 

94-10 

91-42 

91-13 

214  IRON    AND    STEEL    MANUFACTURE. 

Analyses  of  grades  of  certain  classes  of  pig  iron  will  be 
found  on  p.  241. 

By  giving  attention  to  the  temperature  of  the  blast  furnace 
and  the  condition  (whether  basic  or  otherwise)  of  the  slag,  the 
percentage  of  silicon,  of  carbon,  and  of  manganese  may  be 
regulated  fairly  well. 

The  best  system  for  producing  pig  iron  containing  only  a 
small  percentage  of  sulphur  is  to  carefully  select  raw  materials 
which  contain  a  low  percentage  of  sulphur.  This,  however, 
involves  a  high  cost,  and  recourse  must  be  had  to  means  and 
conditions  which  will  cause  much  of  the  sulphur  either  to  go 
off  in  the  gases  or  go  into  the  slag.  The  latter  is  the  less 
objectionable  method.  A  furnace  which  is  working  hot  and 
with  abundance  of  lime  in  the  burden  is  not  so  likely  to  yield 
a  sulphury  pig  iron,  but  if  the  furnace  is  comparatively  cold 
and  the  slag  produced  is  deficient  in  lime,  a  pig  iron  high  in 
sulphur  will  result. 

Carbon  exists  in  pig  iron  in  two  states  at  least  (a)  as 
combined  carbon,  and  (b)  as  graphitic  carbon.  In  the  latter 
condition  the  carbon  is  not  in  chemical  union  with  any  other 
element :  it  exists  in  the  free  state,  and  at  times  in  flakes  so 
large  and  so  loose  that  they  may  be  detached. 

The  percentage  of  carbon  in  the  pig  iron  produced  depends 
very  much  on  the  quantity  and  quality  of  the  fuel.  Apart 
from  other  conditions,  a  furnace  which  is  hot  and  supplied 
liberally  with  fuel  is  likely  to  contain  much  carbon,  especially 
graphitic  carbon ;  and  the  high  temperature  and  the  surplus 
energy  which  that  implies,  having  an  active  reducing  effect, 
tends  to  the  production  of  pig  iron  rich  in  silicon. 

In  "  finishing  materials "  such  as  ferro-silicon,  in  which 
silicon  predominates,  the  carbon  is  not  plentiful,  and  it  exists 
chiefly  in  the  graphitic  state.  Manganese  acts  differently  • 
where  there  is  much  manganese — unless  it  is  interfered  with 
by  silicon — the  percentage  of  combined  carbon  is  higher  than 
in  ordinary  pig  irons.  A  comparison  of  the  analyses  on 
pp.  237  and  238  shows  clearly  these  differences. 

For  the  production  of  a  pig  iron  containing  a  high 
percentage  of  silicon,  the  proper  blast-furnace  conditions 
are: — 


THE    PRODUCTS    OF    THE    BLAST    FURNACE.  215 

(a)  Presence  of  Plenty  of  Siliceous  Matter,  especially  such 
as  can  be  easily  reduced.    Certain  ores  are  prone  to  yield 
highly  siliceous  pig  iron,  even  if  the  percentage  of  silicon 
in  the  ore  is  not  great. 

(b)  A  High  Temperature,  which  means  plenty  of  spare 
energy  in  the  furnace  to  cause  the  reduction  of  much 
silica  (Si02)  to  silicon  (Si). 

(c)  The  Furnace  working  slowly. — This  condition  allows 
more  time  for  the  reduction  to  be  effected. 

(d)  Not   too   much  Lime  in  the   Burden. — If  there  is 
plenty  of  lime  present  the  silica  will  combine  with  it 
and  be  carried  into  the  slag,  but  if  lime  is  comparatively 
scarce  the  free  silica  will  be  left  more  open  to  reducing 
influence. 

There  is  no  intention  to  suggest  that  all  the  above  condi- 
tions will  exist  at  the  same  time,  but  each  one  tends  to  the 
production  of  siliceous  pig  iron.  Contrary  conditions  will 
result  in  the  production  of  a  pig  iron  in  which  the  content  of 
silicon  will  be  comparatively  low. 

For  the  production  of  a  pig  iron  with  much  manganese  in 
it,  it  is  necessary  to  have — 

(a)  A  large  amount  of  manganese  in  the  blast-furnace 
charge. 

(b)  A  high  temperature :  manganese  oxide  in  quantity 
is  more  difficult  to  reduce  than  iron  oxide. 

(c)  Presence    of    abundance    of    lime    in    the    charge. 
Lime,  being  basic,  will  combine  with  the  free  silica,  and 
the  silica  being  thus  satisfied  will  not  so  readily  combine 
with  the  (basic)  oxide  of  manganese  of  the  ore. 

The  blast-furnace  conditions  may  be  briefly  summarised 
thus : — 

To  produce  a  pig  iron 


Fuel  should  be 

Lime  should  be 

High 

5? 

Low 

in  carbon,   . 
silicon,    . 
manganese,     . 
in  sulphur,  . 

Abundant. 
»> 

M 

Not  too  plentiful. 
Abundant. 

}> 

216 


IRON   AND    STEEL   MANUFACTURE. 


Grey  and  White  Pig  Iron. — A  blast  furnace  which  is 
working  on  a  light  burden  (see  p.  203),  or  at  a  high  tempera- 
ture, produces,  as  a  rule,  grey  pig  iron;  that  is,  pig  iron  which 
contains  much  carbon  and  silicon — the  silicon,  as  usual,  causing 
much  of  the  carbon  to  pass  into  the  graphitic  state. 

On  the  other  hand,  a  blast  furnace  which  is  working  on  a 
heavy  burden,  or  at  a  comparatively  low  temperature,  generally 
produces  a  white  pig  iron;  that  is,  a  pig  iron  containing  less 
carbon  and  silicon,  and  in  which  most  of  the  carbon  is 
chemically  combined  with  the  iron. 

Mottled  pig  iron  is  intermediate  in  composition,  and  may 
be  looked  on  as  an  intimate  mixture  of  the  two  kinds. 

Grey  pig  iron  has  a  higher  melting  point  than  white  pig 
iron ;  in  other  words,  it  requires  a  higher  temperature  to  melt 
the  grey  variety.  When  melted,  grey  pig  iron  is  more  fluid 
than  white  pig  iron.  Melted  grey  pig  iron  expands  just 
before  solidifying.  This  enables  it  to  take  a  sharp  impression 
when  cast  in  a  mould,  hence  it  is  most  suitable  for  fine 
castings.  White  pig  iron  does  not  so  expand  before  be- 
ginning to  solidify.  During  melting  and  cooling,  white  pig 
iron  passes  through  a  pasty  stage  which  is  favourable  for 
puddling. 

The  chief  characteristics  of  grey  and  white  pig  iron  from  an 
ordinary  blast  furnace  burden  for  foundry  or  forge  iron  may 
be  conveniently  summarised  and  compared  thus : — 


GREY  PIG  IRON. 
Contains  much  carbon. 

Most  of  the  carbon  is    in    the 
graphitic  state. 

Contains  a  high   percentage    of 
silicon. 

Contains  much  manganese. 

Contains  little  sulphur. 

Average    specific  gravity  about 
71. 

Is  large-grained   (open-grained), 
grey,  soft,  and  tough. 


WHITE  PIG  IRON. 

Most  of  the  carbon  is  combined. 
Does  not  contain  so  much  silicon. 
Does  not  contain  so  much  man- 


Contains  more  sulphur. 

Average  specific    gravity  about 
7*5. 

Is    fine-grained    (close-grained), 
white,  hard,  and  brittle. 


THE    PRODUCTS    OF    THE    BLAST    FURNACE.  217 

GREY  PIG  IRON.  WHITE  PIG  IRON. 


Melting  point,  about  1,400°  C. 

Is  more  fluid  when  melted  than 
is  white  iron. 

Expands  just  before  solidifying. 


Melting  point,  about  1,300°  C. 

Is  not  so  fluid  when  melted  as 
grey  iron  is. 

Passes    into   a   pasty  condition 
when  below  its  melting  point. 


It  must  be  distinctly  understood  that  the  above  table  shows 
the  characteristics  of  average  pig  iron  of  each  kind.  There 
are  exceptions.  The  physical  condition  and  appearance 
(which  may  not  inaptly  be  called  the  texture)  of  a  pig  iron— 
whether  grey,  mottled,  or  white — are  affected  by  its  chemical 
composition,  the  rate  at  which  it  has  been  cooled,  and  by 
other  circumstances.  The  appearance  of  the  fracture  is  not  a 
safe  guide  in  grading  pig  irons.  The  grading  should  be 
arranged  according  to  analyses.  Sometimes  the  grey  pig  iron 
from  a  blast  furnace  actually  contains  less  silicon  than  a  white 
pig  iron  from  the  same  or  a  previous  cast.  A  blast  furnace 
working  smoothly  on  a  proper  burden  is  not  so  likely  to 
produce  such  abnormal  pig  irons,  but  if  a  "slip"  has  occurred 
the  pig  iron  may  easily  show  a  deceptive  fracture.  Swedish 
pig  iron,  which  is  "chilled"  by  being  cast  in  thick  iron 
moulds,  is  white  on  the  under  part  of  the  plate  (or  pig),  while 
the  upper  part  of  the  same  pig  iron  is  grey.  The  bottom 
part  is  hard,  the  upper  part  is  soft.  The  percentage  of  silicon 
is  nearly  the  same  in  each  part,  but  in  the  lower  portion  the 
combined  carbon  predominates.  In  the  upper  part  the  carbon 
is  mostly  in  the  form  of  graphite  in  fine  grains — not  in  scales, 
as  one  finds  it  in  grey  pig  iron  which  has  been  cast  in  sand. 

Grading  of  Pig  Irons.— It  is  customary  to  call  the  richest 
grey  pig  iron  "No.  1."  It  is  the  dearest  of  its  class,  and 
rightly  so,  since,  on  account  of  the  greater  consumption  of 
fuel  used  in  its  production,  it  costs  more.  Pig  iron  which  is 
less  grey  is  called  No.  2,  and  so  the  grading  goes  on  through 
the  mottled  pig  iron  to  the  whitest  of  all. 

Staffordshire  part  mine  pig  iron — which  is  made  chiefly 
from  North  Staffordshire  ore,  Northampton  ore,  and  a  little 
flue  cinder — is  generally  graded  as  mine  foundry  No.  1,  mine 
foundry  No.  2.  mine  foundry  No.  3,  grey  forge,  forge,  strong 
forge,  mottled,  and  white.  Cinder  foundry  pig  iron  is  generally 


218 


IRON    AND    STEEL    MANUFACTURE. 


sold  in  mixed  numbers  1,  2,  and  3.     Very  rarely  cinder  No.  1 


pig  iron  is  ordered, 
mottled,  and  white. 


Other  cinder  pig  irons  are  cinder  forge, 


Fig.  90.— Fracture  of  Grey 
Pig  Iron. 


Fig.  91.— Fracture  of  Mottled 
Pig  Iron. 


Fig.  92.— Fracture  of  White 
Pig  Iron. 


Fig.  93.— Fracture  of  Pig  Iron, 
White  at  Bottom,  Grey  at  Top. 


THE    PRODUCTS    OP   THE    BLAST    FURNACE.  219 

In  Scotland  it  is  usual  to  grade  pig  irons  as  No.  1,  No.  3, 
No.  4,  mottled,  and  white.  Some  makers  quote  No.  2,  and 
all  will  select  it  when  wanted.  Several  ironmasters  have 
their  own  manner  of  grading.  One  grades  thus: — No.  1, 
No.  3,  No.  3  hard,  No.  4,  mottled,  and  white.  Another 
one  grades  No.  1,  No  3  special,  No.  3  soft,  No.  3  foundry, 
No.  3  close,  and  No.  3  hard.  Lots  which  are  sold  under  the 
Scotch  pig-iron  warrant  system  as  Gr.M.B.  are  made  up  in  the 
proportion  of  three-fifths  of  No.  1  and  two-fifths  of  No.  3. 

The  grading  of  pig  iron  in  the  United  States  is  complicated. 
Thirteen  grades  have  been  mentioned  and  nine  grades  are 
well-known,  viz.  : — Silver  grey,  No.  1  soft,  No.  2  soft,  No.  1 
foundry,  No.  2  foundry,  No.  3  foundry,  grey  forge,  mottled, 
and  white.  It  has  been  suggested  that  the  following  six 
grades  should  suffice  : — Silvery  iron,  soft  iron,  foundry  iron, 
grey  forge,  mottled,  and  white.  The  practice  of  purchasing 
pig  iron  by  analysis  has  established  itself  in  the  States,  and  is 
finding  extensive  acceptance.  Other  considerations  must, 
however,  count  as  well  as  composition. 

SLAGS. — The  slag  from  a  blast  furnace  which  is  smelting 
iron  ores  is  made  up  of  the  gangue,  the  fixed  constituents  of 
the  flux,  and  the  ash  of  the  fuel.  All  the  gangue,  except  the 
portion  which  is  reduced,  goes  into  the  slag.  The  fixed  con- 
stituents of  the  flux  includes  all  except  carbon  dioxide,  organic 
matter,  and  water. 

The  quantity  of  slag  will  depend  chiefly  on  the  amount  and 
the  nature  of  the  gangue.  Ores  which  contain  much  gangue 
requiring  plentiful  addition  of  flux  will,  of  course,  yield  more 
slag  than  ore  or  ores  containing  a  comparatively  small  quantity 
of  self-fluxing  gangue.  Self-fluxing  gangue  consists  of  silica 
and  bases  in  such  relative  proportions  that  no  addition  of  flux 
is  necessary  to  produce  a  mixture,  or  slag,  which  can  readily  be 
melted  at  the  working  temperature  of  the  blast  furnace.  The 
amount  of  slag  produced  varies  widely.  It  has  been  stated  as 
between  10  cwts.  and  35  cwts.  per  ton  of  pig  iron  produced. 

Slags  from  blast  furnaces  which  are  producing  white  pig 
iron,  contain,  as  a  rule,  more  silica  than  a  neighbouring 
furnace  which  is  producing  grey  pig  iron.  This  is  quite 
natural.  There  has  not  been  such  an  abundant  reduction  of 


220 


IRON    AND    STEEL    MANUFACTURE. 


silica  during  the  making  of  white  pig  iron,  therefore  more 
silica  must  be  left  free  to  go  into  the  slag. 

The  following  are  approximate  analyses  of  average  slags : — 


Constituents. 

Chemical 
Formulae. 

From 
Clayband 
Ores. 

From 
Cleveland 
Ores. 

From 
Mixed 
Hematite 
Ores. 

Silica,    

Si02 

36 

28 

34 

Alumina,        .... 
Lime,     ..... 

^ 

16 
42 

22 
40 

13 
51 

Magnesia, 
Manganous  oxide, 
Ferrous  oxide, 
Sulphur, 

MgO 
MnO 
FeO 

s 

4 

1 

)      i 

7 
0-2 
0-8 

1 
1 

Alkalies,  &c., 
Calcic  sulphide,     . 

CaS 

I  ' 

2 

... 

L        __ 

100 

100-0 

100 

GASES. — A  working  blast  furnace  emits  an  enormous  volume 
of  gases.  William  Jones  stated*  that  the  gases  from  the 
Scotch  (coal-fed)  blastfurnaces  averaged  over  230,000  cubic 
feet  at  the  temperature  (500°  F.)  at  which  they  left  the  blast 
furnace.  James  Biley  considered  f  that  the  volume  of  gas, 
measured  at  ordinary  temperature  and  pressure,  from  1  ton 
of  coal  measured  130,000  cubic  feet,  while  from  1  ton  of  coke 
the  gases  measured  180,000  cubic  feet  under  like  conditions. 

The  weight  of  the  gases,  per  ton  of  pig  iron  produced,  is 
about  7  tons. 

The  gases  from  the  blast  furnace  were  called  "  waste  gases," 
and  the  term  was  quite  correct  at  one  time.  Now  that,  after 
discharging  fully  their  duties  in  the  blast  furnace,  they  perform 
much  useful  work,  the  term  surplus  gas  would  be  more 
accurate,  but  the  generally  accepted  name — blast-furnace  gas 
— is  sufficient.  Because  of  the  presence  of  certain  constituents, 
the  surplus  gas  is  strongly  reducing.  An  excess  of  powerfully 
reducing  gases  must  be  present  in  the  surplus  gas  or  the  work 
of  the  blast  furnace  could  not  be  carried  on.  Now,  those 


*  Iron  and  Steel  Institute  Journal,  1885,  ii.,  p.  412. 
d.,  1898,  i.,  p.  33. 


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THE    PRODUCTS    OF    THE    BLAST    FURNACE. 


221 


constituents  which  have  reducing  power  are  capable  of  com- 
bining rapidly  with  oxygen  and  evolving  much  heat.  Blast- 
furnace gas  is  therefore  carefully  collected  and  utilised  for 
heat-raising  and  steam-raising. 

The  following  may  be  noted  as  fairly  representative  analyses 


of  blast-furnace  gases  : — 


Constituents. 

Chemical 
Formulae. 

From 
Charcoal  - 
fed 
Furnace. 

From 
Coke-fed 
Furnace. 

From 
Coal-fed 
Furnace. 

Reducing  gases  — 

Carbon  monoxide, 

CO 

25 

28-00 

28-0 

Hydrogen, 
Methane  or  marsh  gas, 

H0 
CH4 

4 

1 

1-00 
0-25 

5-5 
45 

Total  combustible  gases, 

30 

29-25 

38-0 

Inert  or  neutral  gases  — 
Carbon  dioxide,* 

COo 

12 

15-00 

8-6 

Nitrogen,  .... 

N2 

58 

55-75 

53-4 

100 

100-00 

100-0 

Steam-raising  by  means  of  surplus  blast-furnace  gas  may 
be  carried  on  by  burning  the  gas  with  a  regulated  amount 
of  air  in  a  "front"  or  grate  and  combustion  tube  of  an 
ordinary  boiler,  or  by  the  well-known  Babcock  &  Wilcox 
boilers  compactly  enclosed.  RS  shown  in  the  opposite 
illustration. 

But  the  tendency  of  the  times  is  to  utilise  the  gas  by 
generating  power  direct  in  a  gas  engine  rather  than  by 
means  of  steam.  Increased  power  (perhaps  three  or  four 
times  as  much)  may  be  obtained  by  means  of  the  gas 
engine. 

The  gases  from  many  (indeed  nearly  all)  coal-fed  blast 
furnaces  are  condensed  and  scrubbed  so  as  to  recover  the 
ammonia,  tar,  and  oils  from  them.  The  scrubbed  gases  are 
used  for  heat-raising  and  other  purposes. 


*  Under  certain  conditions  carbon  dioxide  acts  as  an  oxidising  gas. 


222 


IRON    AND    STEEL    MANUFACTURE. 


At  one  work  the  blast-furnace  gas 

Distils  the  tar  and  ammonia  liquor, 

Heats  the  hot-blast  stoves, 

Provides  steam  for  the  whole  works, 

Melts  the  steel  in  the  steel  foundry, 

Heats  the  core  stoves  for  three  large  foundries, 

Burns  the  ore  briquettes  in  12 -chamber  kilns, 

Distils  the  coal  for  the  gas  works  supplying  the 

village, 
Supplies  fuel  for  an  enamel  brickwork  a  mile 

away,  &c. 


Fig.  94. — Front  of  Boilers  Fired  with  Blast-furnace  Gaa. 


THE    PRODUCTS   OF   THE    BLAST    FURNACE. 


223 


Fig.  95. — Sketch  Showing  Section  of  Arrangement  for  Utilising 
Blast-furnace  Gas  for  Steam  Raising. 


Fig.  96.— Engine  Worked  by  Blast-furnace  Gas. 


224 


CHAPTER   XXIII. 

NOTES  ON  FUELS,  FLUXES,  REFRACTORY 
MATERIALS,  &c. 

FUEL  is  "anything  that  feeds  a  fire."  A  substance  to  be  of 
service  as  a  fuel  must  be  capable  of  burning  rapidly,  and  of 
giving  forth  much  heat  while  burning.  Cheap  fuel  is  an 
important  point  in  connection  with  manufactures. 

Burning  results  from  the  kindling  of  inflammable  material 
where  air*  in  proper  quantity  has  free  access,  and  combustion 
is  continued  by  the  chemical  combination  of  oxygen  with  the 
fuel.  Slow  combustion  (breathing,  decay,  &c.),  on  the  one 
hand,  and  the  very  rapid  combination  causing  explosion  or 
conflagration,  on  the  other  hand,  do  not  come  within  the 
present  scope. 

The  chief  components  of  solid  fuel  are  : — 

Carbon. 

Hydrogen. 

Compounds  of  carbon  and  hydrogen. 

Oxygen. 

Nitrogen. 

Ash. 

The  three  tirst  are  of  service  because  they  can  combine  with 
oxygen  and  yield  much  heat :  the  remaining  three  are  worse 
than  useless  from  a  heat-raising  point  of  view — they  contri- 
bute nothing,  but  are  heated  by  the  burning  of  the  other 
constituents. 

The  following  simple  experiment  may  help  to  make  clear 
how  the  components  of  a  solid  fuel  act  when  heated  : — Into  a 
small  crucible  put  2  grammes  of  powdered  coal.  Cover  with 
a  lid,  and  apply  heat  from  a  Bunsen  burner  or  other  smokeless 
flame  to  the  bottom  part  of  the  crucible.  In  the  course  of  two 

*  Air  contains  about  one-fifth  of  its  volume  of  the  active  gas  called 
oxygen. 


NOTES   ON   FUELS,    FLUXES,    ETC.  225 

or  three  minutes  take  off  the  lid  and  examine  its  under  part. 
Globules  of  water  should  be  seen.  If  not,  the  experiment  has 
been  hurried  by  too  hot  a  flame,  or  has  not  been  continued 
long  enough.  After  a  trial  or  two  the  correct  conditions  will 
be  found.  Replace  the  lid,  increase  the  heat,  or  set  the 
crucible  further  down  into  the  tip  of  the  flame,  and  allow  to 
remain  for  some  time.  Smoke  will  issue  from  the  crucible, 
and  shortly  afterwards  a  flame  will  appear  round  the  edge  of 
the  lid,  showing  clearly  that  an  inflammable  gas  is  'being 
driven  off  from  the  coal  by  heat.  Continue  the  heating  for 
an  hour  before  removing  from  over  the  flame.  When  the 
crucible  has  become  cold,  examine  the  contents,  which  should 
consist  of  a  black  substance  either  in  powder  or  caked  together 
(coke),  and  which  has  not  been  burned  away  even  on  the 
application  of  prolonged  heat.  Weigh  the  contents  and  re- 
place in  the  crucible.  Then,  with  the  lid  off,  continue  the 
heating.  The  mass  in  the  crucible  will  glow,  and  after  a  time 
a  white  or  coloured  residue  (ash)  will  be  left.  Heat  and  air 
do  not  affect  it.  When  cool,  weigh  the  ash. 

The  experiment  shows  that  the  coal  contained — 

(a)  Water. 

(b)  Matter    which    was    driven   off    (volatilised)   by 
heat,  and,  on  coming  into  contact  with  air,  could  easily 
be  burned.     From  other  experiments  these  are  known 
to  be  hydrocarbons  (which  are  compounds  of  carbon  and 
hydrogen)  and  other  gases. 

(c)  Matter  (fixed  carbon)  which  could  only  be  burned 
by  heating,  with  excess  of  air ;  and 

(d)  A  residue  (ash)  which  could  not  be  burned  off. 

Heat  Value. — When  1  Ib.  of  carbon  enters  into  chemical 
union  with  enough  oxygen  to  form  carbon  dioxide  (C02), 
sufficient  heat  is  generated  to  raise  8,080  Ibs.  of  water  1°  on 
the  Centigrade  thermometer,  or  8,080  Centigrade  heat  units. 
But  if  the  1  Ib.  of  carbon  cannot  have  more  than  enough 
oxygen  to  form  carbon  monoxide  (CO),  the  heat  generated 
is  only  equal  to  2,400  heat  units.*  On  further  oxidation  of 
the  resulting  2J  units  of  carbon  monoxide  (CO)  into  carbon 
dioxide  (C02)  another  5,600  heat  units  are  generated. 

*"Heat  units"  are  also  known  by  the  terms  "calorific  power" 
(Latin,  color  =  heat)  or  "calorific  value." 

15 


226 


IRON    AND    STEEL    MANUFACTURE. 


When  1  Ib.  of  carbon  is  fully  burned,  3f  Ibs.  of  carbon 
dioxide  are  formed  and  about  11  Ibs.  of  nitrogen  accom- 
pany the  necessary  oxygen,  making  about  13-j-  Ibs.  in  all. 
Beyond  the  oxygen  (and  nitrogen)  stated,  an  excess  of  air  is 
necessary  in  practice.  All  these  gases  are  heated  to  the 
temperature  of  the  furnace,  and  thus  a  great  deal  of  heat  is 
carried  away  up  the  chimney.  A  "  draught "  is  created 
thereby. 

The  heat  value,  or  calorific  power,  of  hydrogen  is  34,000 
when  oxidised  under  favourable  experimental  conditions  to 
form  water,  the  chemical  formula  of  which  is  H20 — a  formula 
which  indicates  that  two  atoms  of  hydrogen  have  entered  into 
chemical  union  with  one  atom  of  oxygen.  But  in  practice  the 
water  is  converted  into  steam — which  is  H20  in  the  gaseous 
state.  That  conversion  requires  such  an  expenditure  of 
energy  (or  heat)  that  less  than  29,000  heat  units  are  left 
over.  Every  pound  of  hydrogen  when  burned  combines  with 
8  Ibs.  of  oxygen  to  form  9  Ibs.  of  steam.  Owing  to  the  large 
quantity  of  steam  formed  and  to  the  capacity  of  steam  for 
carrying  off  heat,  the  surplus  heat  derived  is  not  so  large  as 
from  the  burning  of  1  Ib.  of  carbon. 

The  composition  of  solid  fuels  varies  considerably,  but  an 
idea  of  their  composition  may  be  gathered  from  the  following 
table : — 


NATURAL  FUELS. 

PREPARED  FUELS. 

Wood. 

Bitu- 
minous 
Coal. 

Anthra- 
cite. 

Charcoal. 

Coke. 

Fixed  Carbon, 
Hydrocarbons,  Ac., 
Ash, 
Water,    . 

Sulphur  in  the  ash, 

25 
52 

22 

56 
33 
5 
6 

82 
10 
6 
2 

92 
1 
4 
3 

87 
2 
8 
3 

,00 

100 

100 

100 

100 

, 

1 

... 

1 

NOTES    ON    FUELS,    FLUXES,    ETC.  227 

Coals  may  be  classified  thus — 

1.  Bituminous  coal. 

(a)  Caking,  or  coking. 

(b)  Non-caking. 

2.  Anthracite. 

Bituminous  coals  may  burn  either  with  a  long  or  a  short 
flame.  The  long-flame  coal  is  useful  for  reverberatory  fur- 
naces. Anthracite  does  not  produce  much  flame  when  burning. 

Our  coal  deposits  were  formed  from  plants,  and  it  may  be 
instructive  to  briefly  consider  their  formation.  To  begin 
with,  plants,  when  in  life,  decompose  carbon  dioxide  (C02), 
giving  back  oxygen  to  the  air  while  retaining  the  carbon. 
They  also  absorb  water  (H20).  From  carbon  and  water  they 
build  up  cellulose  or  woody  fibre,  the  composition  of  which  is 
C6H1005  or  C6(H20)5.  In  a  byegone  geological  period  im- 
mense forests  were  covered  over,  and  for  long  ages  the  plants 
(blub  mosses,  trees,  &c.)  were  subjected  to  the  influence  of  the 
internal  heat  of  the  earth.*  This  caused  decomposition, 
The  volatile  matters  were  partially  driven  off  and  fixed 
carbon  concentrated.  This  concentration  is  strongly  marked 
in  anthracite.  Most  of  the  ash  is  from  earthy  matter  which 
intermingled  with  the  covered-over  trees,  &c. 

When  coal  which  is  of  a  coking  nature  is  Tiighly  heated  for 
some  time  without  access  of  air,  or  air  in  very  limited  amount, 
it  is  converted  into  coke.  During  coking,  water  and  the 
volatile  hydrocarbons  are  driven  off.  The  result  is  a  further 
concentration  of  carbon  and  the  production  of  a  strong  fuel 
which  is  capable  of  generating  an  intensely  high  temperature. 

Good  coke  does  not  contain  much  volatile  matter  and  not 
more  than  a  moderate  amount  of  ash.  It  is  strong,  lustrous, 
dense,  and  at  the  same  time  porous.  It  must  be  strong  so  as 
to1  withstand  well  the  crushing  of  materials  in  a  cupola  or  a 
tall  blast  furnace.  When  a  coking  oven  is  very  hot,  some  of 
the  liberated  hydrocarbons  become  decomposed ;  hydrogen  is 

*  As  one  descends  a  mine  he  can  hardly  fail  to  note  the  rise  in 
temperature. 


228  IRON   AND   STEEL   MANUFACTURE. 

set  free  and  finely-divided  carbon  is  deposited  on  the  coke. 
The  shining  silvery  lustre  is  taken  as  evidence  of  the  coke 
having  been  prepared  in  a  highly-heated  coke  oven. 

When  coke  is  porous  its  numerous  small  pores  may  become 
filled  with  the  hot  gases  in  the  furnace  and  the  coke  will  burn 
quickly  when  kindled.  Density  along  with  porosity  implies 
that  the  material  comprising  the  walls  of  the  cells,  or  pores, 
is  compact ;  otherwise  the  coke  would  crumble. 

The  favourite  coke  of  many  foundry  and  blast-furnace 
managers  is  made  in  bee-hive  ovens.  Much  coke  is  now  made 
in  retort  ovens  which  are  arranged  in  batteries,  each  coking 
chamber  being  about  33  feet  long,  6  feet  high,  and  1  foot 
6  inches  wide— the  actual  width  depending  on  the  nature  of  the 
coal.  The  crushed  coal  intended  for  coking  is  quickly  dropped 
from  two  2-ton  overhead  hoppers  into  a  hot  coking  chamber. 
In  more  modern  coking  plant  the  crushed  coal  is  compressed  in 
a  mould  and  the  block  is  charged  into  the  hot  coking  chamber. 
The  gases  which  come  off  are  scrubbed  to  extract  the  ammonia 
and  other  valuable  "  residuals,"  and  then  passed  along  with  a 
regulated  amount  of  air  to  be  ignited  and  burned  in  passages 
at  the  sides  and  underneath  the  coking  chamber.  When  the 
coking  is  finished  a  ram  pushes  out  the  block  of  coke. 

Charcoal  is  prepared  by  drying  and  heating  wood,  under  a 
covering  of  non- combustible  matter,  or  in  a  kiln,  till  it  it 
charred  as  black  as  coal.  The  volatile  matters  (water  anc 
hydrocarbons)  are  nearly  all  driven  off.  There  is  less  ash  ir 
charcoal  than  in  coal. 

FLUXES. — Substances  which  are  to  be  used  for  fluxing4 
must  be  of  a  chemical  nature  opposite  to  that  of  the  substances 
which  are  to  be  fluxed.  The  chief  idea  is  to  form  from  th< 
gangue  a  fluid  slag.  If  silica  (which  is  of  an  acid  nature 
predominates  in  the  gangue  of  an  ore,  the  flux  must  be  basi 
(see  p.  26).  Lime  (CaO)  being  cheap  is  freely  used.  Mono 
silicate  of  lime  (2 CaO,  Si02)  is  a  common  constituent  of  blast 
furnace  slags.  But  if  a  furnace  temperature  is  not  equal  to  th 

*  The  words  "fluxing"  and  "fluid"  are  from  the  Latin  and  signif 
flowing. 


NOTES   ON    FUELS,    FLUXES,    ETC.  229 

task  of  melting  a  compound  of  such  high  melting  point,  a  base 
which  will  form  a  compound,  or  slag,  of  lower  melting  point 
must  be  used  in  order  to  work  a  metallurgical  process  success- 
fully. In  such  a  case  ferrous  oxide  (FeO)  will  be  supplied,  so 
that  the  silica  may  form  with  it  silicate  of  iron  (2FeO,  Si02), 
which  melts  at  a  moderate  furnace  temperature.  Ferrous 
silicate  is  the  chief  constituent  of  the  slag  from  a  puddling 
furnace.  The  puddling  furnace  cannot  be  relied  on  to  melt 
silicate  of  lime,  and,  besides,  lime  has  been  found  to  interfere 
seriously  with  the  quality  of  wrought  iron.  It  is,  however, 
used  sparingly  with  success.  Lime,  being  a  cheaper  flux  than 
iron  oxide,  is  used  where  enough  heat  can  be  had,  as  in  blast- 
furnace practice  and  in  the  manufacture  of  steel. 

Silicates  with  two  bases  are,  as  a  rule,  more  fusible  than 
those  containing  either  of  the  bases  singly.  When  required, 
a  second  substance  is  selected  to  assist  in  the  fluxing  of  gangue. 
Of  this  a  well-known  instance  is  the  charging  of  aluminous  ore 
along  with  limestone  when  smelting  English  hematite  ore.  The 
result  is  a  slag  containing  silicate  of  lime  and  alumina.  This 
compound  silicate  melts  at  a  lower  temperature,  and  so  helps 
blast-furnace  working.  In  smelting  clay-band  ironstone  it  is 
not  necessary  to  add  more  than  one  fluxing  material,  because 
clay  (which  constitutes  the  bulk  of  the  gangue)  contains  both 
silica  and  alumina.  Addition  of  the  necessary  lime,  therefore, 
leads  to  the  formation  of  the  compound  silicate  of  lime  and 
alumina. 

SUMMARY  OF  COMMON  FLUXES. 

Silica     .         .  acts  as  a  flux  for  ferrous  oxide. 
Ferrous  oxide  „  „       silica. 

Silica      .  „  „       lime. 

Lime  „          „       silica. 

Lime      .  „  clay. 

Clay       .         .  „  „       lime. 

Alumina  (A1203)  may  act  as  a  base  when  silica  predominates, 
or  may  act  as  an  acid  when  lime  is  the  chief  component. 


230  IRON    AND    STEEL   MANUFACTURE. 

Magnesia  (MgO)  may,  in  part  at  least,  be  substituted  for 
lime.  Its  silicate  does  not  melt  quite  so  readily,  but  magnesia 
tends  to  form  a  hard  slag  which  can,  when  cold,  be  usefully 
applied.  Under  certain  conditions  magnesia  readily  combines 
with  sulphur. 

Manganons  oxide  (MnO)  may  also  with  advantage  replace 
some  of  the  lime. 

Ferrous  oxide  (FeO)  is  out  of  place  in  blast-furnace  slag. 

Fluor  spar  is  useful  for  increasing  the  fluidity  of  certain 
slags  and  is  very  helpful  as  a  desulphuriser.  Its  use  in  iron 
and  steel  works  is  steadily  increasing. 

REFRACTORY  MATERIALS  for  metallurgical  purposes  are 
such  as  successfully  withstand  chemical,  mechanical,  and 
thermal*  actions. 

They  are  required  to  resist  combination  with  oxygen,  thus 
differing  from  fuels.  They  are  required  to  resist  chemical 
union  with  gangue  or  slag,  thus  differing  from  fluxes.  They 
should  also  be  able  to  withstand  continued  exposure  to  in- 
tense heat,  and  also  sudden  changes  of  temperature,  without 
softening,  cracking,  or  changing  shape. 

Refractory  materials  are  chiefly  composed  of 


I. 

Silica,          .... 
Titanic  oxide, 

.  Si02 
.  Ti02 

II. 

Alumina,     .... 
Chromic  oxide,    . 
Ferric  oxide,        , 

.  A1A 
.  CrA 
.  FeA 

III. 

Lime,          .... 
Magnesia,    . 

.  CaO 
.  MgO 

IV.  Impurities — 

Ferrous  carbonate,        .         .         .  FeC03 

Iron  pyrites,        .         .         .         .  FeS 

Potash, K20 

Soda, Na,0 

*  From  Greek  therm6  =  heat. 


NOTES   ON    FUELS,    FLUXE8,    ETC.  231 

Class     I.  =  acid  substances. 
Class    II.  =  neutral     „ 
Class  III.  =  basic        „ 

Class  IV. — Lime  and  magnesia  are  amongst  the  most 
fatal  impurities  of  fireclays.  All  the  iron  compounds  are 
injurious  to  firebricks,  but  the  most  serious  is  iron  pyrites 
(FeS2).  When  a  firebrick  is  kiln-burnt  this  loses  half  its 
sulphur  and  forms  the  highly-fusible  ferrous  sulphide,  which 
gradually  combines  with  silica  and  fuses.  Potash  and  soda 
are  alkaline  substances,  and  presence  of  either  or  both  in 
more  than  minute  quantities  is  highly  injurious  to  acid 
refractory  materials  and  in  a  lesser  degree  to  the  others. 

A  good  refractory  material  is  simple  in  its  composition  ; 
one  substance,  or  substances  of  a  like  constitution  and  chemical 
nature,  must  largely  predominate  in  its  composition,  with 
enough  component  of  an  opposite  chemical  nature  to  hold 
it  together,  yet  not  enough  to  cause  it  to  flow  or  soften  at  the 
temperature  of  the  furnace  or  lining  for  which  it  is  used. 
Take  as  examples  the  lining  and  the  walls  of  a  Siemens 
furnace.  The  furnace  is  worked  at  a  very  high  temperature. 
The  working  lining  is  made  up  of  silver  sand,  which,  being 
very  pure,  does  not  even  frit  with  the  intense  heat  of  the 
furnace.  A  small  quantity  of  loam  or  of  impure  sand  (which 
can  be  melted  at  the  furnace  temperature)  is  added  as  a 
binding  material.  The  bricks  of  which  the  walls  and  the 
roof  are  built  require  a  stronger  binding,  and  this  is  sup- 
plied by  mixing  about  2  per  cent,  of  lime,  made  into  a 
thick  cream  with  water,  to  the  crushed  siliceous  rock  of  which 
the  bricks  are  made.  Fireclay,  on  the  other  hand,  usually 
contains  more  binding  material  (chiefly  alumina)  than  is 
required. 

In  selecting  a  refractory  material  for  a  furnace  one  of  the 
first  considerations  is  the  chemical  nature  of  the  slag.  Will 
it  be  acid  or  basic  ?  A  refractory  substance  of  the  same 
nature,  or  a  neutral  substance,  must  be  selected.  The  amount 
of  binding  material  must  be  determined  by  the  temperature 
at  which  the  furnace  is  to  be  worked. 


232  IRON    AND    STEEL   MANUFACTURE. 

The  chief  acid  refractory  materials  used  in  iron  and  steel 
works  are : — 

Silver  Sand,  largely  imported  from  Belgium;  ordinary  brown 
sand,  and  crushed  Dinas  (South  Wales)  rock. 

G-anister. —  Found  abundantly  near  Sheffield.  In  its 
composition  silica  largely  predominates,  but  it  also  has  in 
itself  enough  binding  material  to  enable  it  to  hold  firmly 
together  while  enduring  the  commotion  and  the  heat  incidental 
to  a  Bessemer  blow. 

Fireclay  which,  as  already  noted,  is  over-rich  in  binding 
material,  and  suffers  in  its  heat-resisting  qualities  in 
consequence. 

Clays  of  greater  purity  than  fireclays. 

Fire-stones,  which  are  capable  of  withstanding  great  heat 
and  considerable  alterations  of  temperature  without  cracking. 

Silica  Bricks. —  These  are  made  by  mixing  siliceous 
(quartzose)  rock — which  has  been  broken  and  crushed — with 
cream  of  lime;  moulding,  drying,  and  kiln-firing.  When 
broken,  these  bricks  show  a  rough  fracture — pieces  of  quartz 
showing  up  distinctly  amongst  the  finer  particles  and  the 
binding  of  lime.  Prominent  yellowish  spots  indicate  the 
presence  of  iron  oxide  in  very  small  amount.  The  bricks  are 
tender  when  cold ;  they  must  be  handled  carefully,  and  kept 
from  exposure  to  damp.  When  heated  they  expand,  and 
they  are  not  so  tender  as  when  cold. 

G-anister  Bricks  resemble  silica  bricks  in  material,  method 
of  manufacture,  and  general  character. 

Firebricks  are  made  by  selecting,  tempering  (or  weathering), 
grinding,  and  sifting  the  fireclay,  mixing  it  with  water, 
moulding,  drying,  and  then  kiln-firing  at  a  temperature  almost 
approaching  to  whiteness.  The  bricks  are  allowed  to  cool 
down  slowly  in  the  kiln  after  the  fire  has  been  withdrawn. 

It  is  usual  to  incorporate  sand,  or  old,  clean  bricks,  in  order 
to  diminish  shrinkage  and  increase  their  power  of  resisting 
heat  Coke  dust  is  sometimes  added. 

Firebricks  contract  during  drying  and  firing;  they  thus 
differ  from  silica  bricks,  which  expand  during  burning  and 
also  when  in  use.  When  broken  across,  firebricks  show  a 
much  finer  grain  than  silica  bricks. 


HOTES   ON    FUELS,    FLUXES,    ETC. 


233 


The  following  table  shows,  approximately,  the  composition 
of  the  chief  acid  refractory  materials: — 


Constituents. 

Chemical 
Formulae. 

White 
Sand 
(Dried). 

Gan- 
ister. 

Fire- 
clay. 

Silica 
Brick. 

Fire- 
Brick. 

Silica, 

Si02 

98-5 

94-6 

56-7 

96-0 

65-0 

Alumina,   . 

A1A 

1-0 

1-5 

30-0 

1-0 

31-0 

Ferric  oxide, 
Ferrous  oxide, 

Fe20 
FeO 

}... 

1-0 

1-5 

1-0 

2-0 

Lime, 

CaO 

J 

0-6 

1-0 

1-7 

1-0 

Magnesia,  . 

MgO 

0-5 

o-i 

0-2 

o-i 

0-3 

Alkalies—                      ( 
Potash  and  soda,      \ 

K20  1 
Na^O/ 

L 

0-2 

0-6 

0'2 

0-7 

Water, 

2-0 

10-0 

... 

100-0 

100-0 

1000 

100-0 

100-0 

Basic  Refractory  Materials  have  been  referred  to  at  some 
length  in  Chapters  ix.  and  xii.,  and  a  table  of  analyses  appears 
on  p.  85. 

Dolomite  is  not  of  a  basic  nature  until  its  carbon  dioxide  * 
(C02)  has  been  driven  off  by  calcination.  Some  firms  pur- 
chase calcined  dolomite.  This  saves  a  considerable  amount 
on  railway  carriage,  but  there  is  danger  of  deterioration  by 
damp  during  transit.  Dolomite  bricks  are  usually  made  in  steel 
works.  Magnesia  bricks  are,  as  a  rule,  bought  ready  made. 

Magnesia  Bricks,  which  are  very  dense,  are  composed  of 
burnt,  ground  magnesite,  and  may  be  bound  with  tar,  strongly 
pressed,  and  kiln-fired.  These  are  dark  coloured.  Other 
brands  are  bound  with  magnesic  chloride,  and  have  a  ruddy 
colour,  due  to  the  presence  of  a  little  ferric  oxide.  These, 
when  fractured,  show  a  grain  resembling  firebrick.  Some 
brands  contain  more  than  90  per  cent,  of  magnesia. 

Neutral  Refractory  Materials  include  chrome  iron  ore, 
bauxite,  and  carbon. 

Chrome  Iron  Oref — the  chief  components  of  which  are  an 
oxide  of  chromium  (Cr203)  and  ferrous  oxide  (FeO) — may  be 
used  in  the  form  of  lumps  cemented  in  position  with  fine 


Sometimes  spoken  of  as  carbonic  acid.       t  See  analysis  on  p.  24tp» 


234  IKON    AND    STEEL   MANUFACTURE. 

ore  and  tar.  Bessemer  converters  thus  lined  last  remarkably 
well. 

Chrome  Bricks  are  made  of  crushed  chrome  iron  ore  mixed 
with  tar,  pressed,  and  kiln-fired.  They  are  black  or  of  a  deep 
purple  colour,  and  show  a  moderately  rough  fracture  when 
broken  (see  analysis  on  p.  245). 

Bauxite  Bricks  are  made  of  crushed  bauxite,  and  have  clay 
for  a  binding  material.  In  colour  they  are  yellowish-brown. 
They  are  moderately  dense  and  externally  firm.  Their  frac- 
ture may  perhaps  be  described  as  resembling  oatmeal  of 
medium  fineness.  The  fractured  parts  may  be  worn  away  by 
rubbing  with  the  finger  tips  (see  analysis  on  p.  245). 

Carbon  is  a  strictly  neutral  substance.  It  withstands  a 
high  temperature  if  oxygen  has  not  access  to  it.  Where  the 
conditions  inside  a  furnace  are  non-oxidising,  carbon  does  not 
burn. 

During  the  working  of  an  iron-smelting  blast  furnace,  a 
"carbonaceous  concrete"  is  formed  in  the  bosh.  It  is  this 
concrete  which  protects  the  brickwork  from  the  fluxing  action 
of  the  slag.  According  to  the  late  Sir  I.  Lowthian  Bell,  "  the 
solvent  power  of  the  slag  over  the  brick  was  almost  as  much 
as  the  solvent  power  of  water  over  sugar."*  The  carbonaceous 
concrete  has  been  found  to  be  several  inches  thick,  and  to 
contain  about  46*6  per  cent,  of  carbon.  Bricks  of  similar 
composition  have  been  used  for  blast-furnace  boshes.  In 
percentage  of  carbon  the  blast-furnace  "concrete"  does  not 
differ  much  from  ordinary  graphite  crucibles. 

Plumbago  or  graphite  is  used  in  the  manufacture  of 
crucibles  and  for  facing  moulds  for  iron  and  steel  castings. 
In  composition  plumbago  varies  over  a  wide  range.  The 
following  figures  may  be  accepted  as  representing  fair  average 
quality : — 

Fixed  carbon,          .         .         .77  per  cent. 
Volatile  matters,  3       „ 

Ash,      .         .         .         .         .       20       „ 

100 
•Iron  and  Steel  Institute  Journal,  1887,  ii.,  117. 


NOTES    ON    FUELS,    FLUXES,    ETC.  235 

DEOXIDISING  AND  RECARBURISING  MATERIALS.  —  The 
following  notes  are  added  to  supplement  the  references  to 
those  in  preceding  chapters  : — 

Spiegel-eisen  is  a  compound  German  word  signifying 
"  mirror-iron."  It  is  highly  crystalline,  and,  when  fractured, 
displays  large  brilliant  plates — hence  the  name.  It  is  made 
in  blast  furnaces,  and  cast  in  pigs  or  in  slabs.  It  may,  with 
comparative  ease,  be  broken  into  fragments  (crystals)  which 
are  very  hard  and  difficult  to  powder,  and  it  is  not  easily 
melted.  The  trade  practice  is  to  charge  it  into  the  converter 
in  the  liquid  state  or  into  the  furnace  (not  into  the  ladle)  in 
a  highly-heated  condition. 

As  the  percentage  of  manganese  increases,  there  is  a  slight 
rise  in  the  percentage  of  carbon.  See  analyses  on  p.  237. 

Ferro-manganese. — The  percentage  of  manganese  is  higher 
in  ferro-manganese  than  in  spiegel-eisen.  It  was  originally 
made  in  crucibles ;  afterwards  it  was  manufactured  in  a 
reverberatory  furnace.  Now  it  is  regularly  made  in  blast 
furnaces  from  ores  containing  much  manganese,  and  a  richer 
variety  is  manufactured  in  electric  furnaces.  Ferro-manganese 
is  grey,  finely  granular,  moderately  hard,  and  is  more  friable 
(that  is,  more  easily  broken)  than  spiegel-eisen. 

The  percentage  of  carbon  increases  slightly  as  the  manganese 
increases.  See  analyses  on  p.  237. 

As  stated  in  previous  chapters,  ferro-manganese  is  used  for 
mild  steels,  and  spiegel-eisen  is  added  for  medium  (higher 
carbon)  steels,  because  the  quantity  of  ferro-manganese 
required  to  give  to  the  steel  a  low  percentage  of  carbon  will 
do  so  without  yielding  more  than  the  desired  percentage  of 
manganese.  On  the  other  hand,  the  amount  of  spiegel-eisen 
which  would  give  to  the  steel  the  required  percentage  of 
manganese  would  yield  a  greater  amount  of  carbon. 

To  make  this  more  clear — 

100  Ibs.  of  60  per  cent,  ferro-manganese  would  contain 
60  Ibs.  of  manganese  and  about  6J  Ibs  of  carbon. 

400  Ibs.  of  15  per  cent,  spiegel-eisen  would  contain  60 
Ibs.  of  manganese  and  about  17|  Ibs.  of  carbon. 


236  IRON    AND    STEEL    MANUFACTURE. 

Spiegel-eisen  usually  contains  from  15  to  25  per  cent,  of 
manganese,  ferro-manganese  contains  over  40  per  cent. 

Silicon  is  useful  for  promoting  soundness  in  steel  castings 
and  in  steel  ingots.  It  appears  to  have  the  power  of  increasing 
the  solubility  of  carbon  monoxide,  thus  lessening  the  tendency 
to  cause  blow-holes  by  keeping  the  gas  in  the  occluded  state 
until  after  the  steel  has  solidified.  The  beneficial  effects  of 
silicon  have  been  recognised  in  iron  foundries  since  1884. 
Certain  pig  irons  containing  silicon  in  noted  amount  (known 
as  glazed  pigs,  blazed  pigs,  and  silky  pigs)  are  used  as 
softeners.  Good,  sound  iron  castings  may  be  made  by  the 
judicious  mixing  of  proper  quantities  of  softener  with  pig  irons 
which  are  of  themselves  too  white  for  foundry  purposes.  Pig 
iron  very  rich  in  silicon  is  now  made  in  blast  furnaces,  and 
is  called  ferro-silicon :  if  also  rich  in  manganese  it  is  called 
silico-spiegel.  Analyses  are  noted  on  p.  238. 

Very  rich  silicon  alloys  are  now  made  in  electric  furnaces. 

Aluminium  —  a  silver- white,  soft,  and  remarkably  light 
metal,  which  is  prepared  in  a  fair  state  of  purity  in  electric 
furnaces — possesses  marvellous  powers  for  inducing  soundness 
in  ingots.  Its  presence  even  in  small  amount  lessens  segrega- 
tion— a  fact  pointed  out  by  Pourcel  some  years  ago,  and 
amply  confirmed  by  Benjamin  Talbot. 

An  alloy  containing  the  three  valuable  components — silicon, 
aluminium,  and  manganese — is  made  by  Messrs.  Blackwell,  of 
Liverpool. 


237 


APPENDIX. 


ANALYSES   OF   FINISHING  MATERIALS, 
SOFTENERS,  ORES,  &c. 

SPIEGEL-EISEN. 


Constituents. 

Chemical 
Symbols. 

* 

Combined  carbon, 
Manganese,   .... 

Silicon, 

c 

Mn 

Si 
P 

4'27 
8-11 
0-11 
0-08 

4'76 
19-67 

•83 
•08 

s 

•01 

Iron,          

Fe 

87-40 

A 

99-97 

100-00 

FERRO-MANGANESE. 


Constituents. 

Chemical 
Symbols. 

* 

* 

Combined  carbon,? 
Manganese, 

Silicon, 
Sulphur,     . 
Phosphorus, 
Copper, 
Iron,  . 

C 

Mn 

Si 
S 
P 
Cu 
Fe 

5-63 
41-82 
0-42 

6-io 
si'-9o 

5-90 
60-58 
0-93 
0-007 
0-19 

"A 

6-17 
71-32 
1-12 

0-162 
0-33 
20-65 

6-38 
81-35 

0-88 
Trace. 
0-23 

A 

99-87 

100-000 

99-752 

100-00 

*  Analyses  by  Mr. 
A  By  difference. 


T.  E.  Holgate. 


Including,  in  some  instances,  a  little  finely-divided  graphite.  Mr.  T.  W.  Hogg, 
Newburn,  found  beautiful  crystals  of  nitro-cyanide  of  copper  in  the  residue  undis- 
solved  in  acid.  These  are  also  found  in  bear,  which  is  an  accumulation  of  iron,  <fec., 
in  the  lowest  part  of  a  blast  furnace. 


238 


APPENDIX. 


FERRO-SILICON.  * 


Constituents. 

Chemical 
Symbols. 

Graphitic      ) 
carbon,      \ 

c 

2-40 

1-70 

1-20 

0-62 

0-55 

Combined      ) 
carbon,       ) 

c 

0-14 

0-11 

0-23 

0-35 

o-ii 

Total  carbon, 

c 

2-54 

1-81 

1-43 

0-97 

0-66 

Manganese,  . 

Silicon,      . 

Mn 
Si 

3-25 
8-54 

2-16 
10-18 

1-95 
14-00 

2-29 
1613 

1-07 
17-80 

Sulphur, 

S 

0-064 

0-055 

0-078 

0-050 

0-041 

Phosphorus,  . 

P 

0-047 

0-104 

0-076 

0-090 

0-115 

Iron, 

Fe 

A 

A 

A 

A 

A 

100-000 

100-000 

100-000 

100-000 

100-000 

SILICON-SPIEGEL. 


Constituents. 

Chemical 
Symbols. 

Graphitic  carbon,     . 

C 

0-33 

0-67 

1-13 

0-90 

Combined      ,  , 

C 

1-85 

0-98 

0-29 

0-30 

Total       ,, 

C 

2-18 

1-65 

1-42 

1-20 

Manganese,  . 
Silicon,  . 

Mn 

Si 

19-64 
10-74 

19-74 
12-60 

22-98 
14-19 

24-36 
1594 

Phosphorus, 
Iron, 

P 
Fe 

0-074 
67-56 

0-080 
66-10 

0-095 
61-60 

0-085 
58-30 

100-194 

100-17 

100-285 

99-885 

The  above  analyses  are  by  Mr.  T.  E.  Holgate,  Darwen.  Absence  of 
sulphur  may  be  noted.  The  author  of  this  book  did  not  find  more  than 
traces  of  that  element  in  any  of  the  many  samples  he  examined.  He 
found  consignments  from  various  makers  to  average  over  0'2  per  cent, 
of  phosphorus,  although  samples  with  0'08  per  cent,  of  phosphorus 
were  not  wanting. 


*  Analyses  by  Mr.  T.  B.  Holgate. 

A  Iron  by  difference— not  stated  in  Mr.  Holgate's  analyses. 


APPENDIX. 


239 


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APPENDIX. 


p;  p  ^H  r-C5O(N  (N  0>O  >p -71       » 


APPENDIX. 

COMPOSITION  OF  SCOTCH  Pio  IRON. 


Constituents. 

Chemical 
Symbols. 

No.  1. 

No.  3. 

No.  3. 
Hard. 

Verge. 

Graphitic  carbon, 

c 

3-46 

3-14 

2-93 

2-66 

Combined      ,, 

c 

0-25 

0'38 

0-47 

•55 

Total       „ 

c 

3-71 

3-52 

3-40 

3-21 

Silicon,       . 

Si 

3-39 

2-43 

1-64 

1-39 

Phosphorus, 

p 

0-91 

091 

0-92 

1-27 

Sulphur,     . 

s 

0-03 

0-03 

0-04 

0-06 

Manganese,        . 

Mn 

1-78 

1-62 

1-49 

1-28 

Iron,  .... 

Fe 

A 

A 

A 

A 

100-00 

100-00 

100-00 

100-00 

CLEVELAND  PIG  IRON  (MUNNOCH).* 


Grade 

Graphitic 
Carbon. 

Combined 
Carbon. 

Silicon. 

Phos- 
phorus. 

Sul- 
phur. 

Man- 
ganese. 

Iron. 

No.  1, 

3-30 

0  10 

3'50 

1-60 

•02 

0-65 

,,2,          .          . 

3-20 

0'15 

3-30 

1-57 

•03 

0-65 

,,3, 

,,    4  Foundry,  . 

3-00 
2-85 

0'30 
0-40 

2-75 
2-25 

1-57 
1-55 

•05 

•08 

0-60 
0-55 

1 

,,    4  Forge, 

2-50 

0-70 

1-75 

1-57 

•13 

0-50 

£ 

Mottled,     . 

1-77 

1-30 

1-10 

1-58 

•25 

0-30 

White, 

Nil. 

3-05 

0-75 

1-60 

•45 

0-20 

A  By  difference. 

*  Table  of  ideal  analyses,  Cleveland  Institution  of  Engineers,  February  1005. 

16 


242 


APPENDIX. 


ANALYSES  or  ORES. 


Constituents. 

Chemical 
Formulae. 

Stafford- 
shire 
Pottery 
Mine. 

Stafford- 
shire 
Pottery 
Mine. 
Calcined. 

Froding- 
ham  Iron 
Ore. 

Mid 
Lincoln- 
shire 
Iron  Ore. 

Ferrous  oxide,    . 

FeO 

42-18 

6-43 

... 

Ferric         ,, 

Fe203 

6-29 

80-88 

44-66 

60-91 

Oxide  of  manganese,  . 

MnO 

2-93 

1-85* 

2-32 

traces 

Silica, 

SiOa 

1-50 

3-00 

738 

13-24 

Alumina,    . 

A120, 

0-22 

0-16 

5-95 

8-03 

Lime,          .         . 

CaO 

4-20 

4-10 

18-27 

1-60 

Magnesia,  . 

MgO 

1-80 

1-30 

3-51 

0-06 

Phosphoric  acid, 

PA 

0-70 

1-15 

0-68 

1-02 

Sulphuric       ,, 

SOS 

1-02 

1-15 

0-06 

0-03 

Bituminous  matter,    . 

) 

... 

Combined  water, 
Carbon  dioxide,  . 

H20 

C02 

V39-29 

... 

13-29 
3-82 

|  15-35 

Loss  on  ignition, 
Metallic  iron, 

Fe 

... 

0-31 

... 

100-13 

100-33 

99-94 

100-24 

37*20 

61-60 

31-26 

42-64 

*  Oxidised  to  Mn304. 


APPENDIX. 


243 


c 
< 
pq 

I 


'oo 


8 


CD  CO  O  <N  ^H  O  I^H  pli      :  O  CO 
»0  CO 


8 


~  :°8 


:  QO  —  <  o  o  o  oo  o  o  o 


ooo  oco  A- 


CD  •<*  O  O  U5  O  O  If5  CO        »O 

:  O5  F^H  o  '-H  o  oo  o  o  o    •  oo 


8 


n  si  'i'lrfl 


.2  ® 
x^ 


2."   c3   b 
H  i  s 

u)^  5  •§  »£S  *5  *» 


" 


c.2 


1! 

ss. 

11 

If 

»is 


IB 
IP 

III 


Uj 

^l*1 

J 


244 


APPENDIX. 


IBON  ORBS  MINED  NEAR  THE  MEDITERRANEAN  SEABOARD. 


Constituents. 

Chemical 
Formulae. 

Cartagena 
Ore. 

Garrucha 
Ore. 

Elba  Ore. 

Ferric  oxide, 

Fe203 

72-05 

79-46 

81-14 

Ferrous  oxide, 

FeO 

Nil 

2-64 

Manganese  oxide, 

Mn804 

2-96 

2-40 

0-20 

Silica,. 

Si02 

4-30 

7-25 

3-58 

Alumina,     , 

A1A 

0-80 

0-27 

2-85 

Lime,  .... 

CaO 

7-28 

2-34 

o-io 

AJagnesia,    . 

MgO 

1-30 

0-54 

o-io 

Phosphoric  acid,  . 

PA 

0-03 

0-04 

0-04 

Sulphuric  oxide,  . 

S03 

0-03 

0-28 

0-13 

Carbon  dioxide,  . 
Combined  water, 

C02 

H20 

7-10 
4-00 

|     7-04 

6-97 

Moisture,    ... 
Iron  in  dried  ore, 

H30 

... 

1-95 

99-85 

99-62 

99-70 

50-75 

55-62 

59-95 

,,        ore  as  received, 

47-87 

49-62 

58-85 

Phosphorus  in  ore, 

0-013 

0-017 

0-017 

APPENDIX. 


245 


COMPOSITION  OF  BRICKS. 

The  following  are  analyses  of  good  quality  bricks  as  supplied  to  steel 
works  by  British  firms  : — 


Constituents. 

Chemical 
Formulae. 

Magiiesite  Bricks.* 

Magnesia, 

MgO 

94-24 

91  -32 

91-50 

CaO 

0-64 

1-40 

2-10 

Silica,  
Alumina,       . 
Ferric  oxide, 

Si02 
A1A 

Fe203 

3-20 

}»* 

5-30 
1-80 

0-35 
6-05 

Alkalies  —  potash  and  soda,  . 

/K20      \  ft.1R 
1  Na20     £  C 

o-is{ 

not  esti- 
mated. 

100-00 

10000 

100-00 

Constituents. 

Chemical 
Formulas.        Bauxite  Brick. 

Chrome 
Brick.* 

Silica,   .         . 

Si02 

3-50 

35-80 

5-20 

Titanic  oxide, 

TiOo 

3-08 

3-70 

0-50 

Alumina,       .... 

A1203 

51-40 

55-80 

13-90 

Chromic  oxide, 

Cr203 

53-66 

Ferric  oxide, 
Ferrous  oxide, 

Fe203 
FeO 

38-37 

1  3-40 

16-20 

Lime,    ..... 

CaO 

2-46 

0-90 

0-78 

Magnesia,      .... 

MgO 

0-79 

Sundries 

9-22 

Alkalies  —  potash  or  soda,     . 

(K20 
\Na20 

|  0-40 

not  esti- 
mated. 

0-54 

100-00 

100-00    1  100-00 

CHROME  IRON  ORE. — COMPOSITION  OF  AVERAGE  SAMPLE. 


Constituents. 

Chemical 
Formulae. 

Silica,  
Titanic  oxide,       ..... 

Si02 
TiO., 

1      2-00 

Al,03 

19-25 

Chromic  oxide,     ..... 
Ferrous  oxide,      
Lime,   ....... 
Magnesia,     ...... 
Loss  on  ignition  —  combined  water,  &c., 

S5P 

CaO 
MgO 

41-67 
14-70 
3-75 
17-66 
097 

100-00 

•  Tarry  matter  (about  5  per  cent.)  for  binding  was  burnt  off  before  making  analyses. 


246 


APPENDIX. 


ANALYSES  OF  GASES. 
PRODUCER  GAS. 


Constituents. 

Chemical 
Formulae. 

Scotch 
Steel 
Work.* 

American 

Steel  Work. 

Reducing  gases  — 
Carbon  monoxide, 
Hydrogen, 
Methane  or  marsh  gas, 

Total  combustible  gases, 

CO 
H.2 
CH4 

25-7 
11-8 
2-3 

16  5 
8-6 
2-7 

22-3 

28-7 
1-0 

39-8 

27-8 

52-0 

Inert  or  neutral  gases  — 
Carbon  dioxide, 
Nitrogen,  .... 

CO, 

N2~ 

6-3 
53-9 

9-3 
62-9 

6-1 
41-9 

100-0 

100-0 

100-0 

WATER  GAS  AND  NATURAL  GAS. 


Constituents. 

Chemical 
Formulae. 

Water  Gag. 

Natural  Gas. 

Approximate 

Approximate 

Average. 

Average. 

Reducing  gases  — 

Hydrogen, 
Carbon  monoxide, 

& 

49-00 
44-00 

22-00 
0-60 

Methane  or  marsh  gas,      . 

CH4 

0-50 

67-00 

Ethylene  or  olefiant  gas,  . 
Ethane  or  ethyl  hydride,  . 

C2H4 
C2H6 

... 

1-00 
5-00 

Total  combustible  gases, 

93-50 

95-60 

Other  gases- 

Carbon  dioxide, 

C02 

3-25 

0-60 

Nitrogen,  .... 

No 

3-25 

3-00 

Oxygen,     .... 

0, 

... 

0-80 

100-00 

100-00 

*  Steam-urged  producer,  fed  with  bituminous  coal  slack. 


APPENDIX. 


247 


AMERICAN  IRON  ORES. 

The  American  continent  is  rich  in  iron  ores,  and  in  the  fuels,  fluxes, 
and  refractory  materials  necessary  for  extracting  iron  and  for  carrying 
on  the  manufacture  of  iron  and  steel. 

The  richness  of  their  virgin  fields,  the  enterprise  of  the  inhabitants, 
and  the  rapid  development  in  many  directions  of  this  great  continent 
have  contributed  to  the  enormous  expansion  of  the  iron  and  steel  trades. 

Analyses  of  some  of  the  chief  iron  ores  are  noted  on  this  and  the 
following  pages.  On  this  page  the  figures  were  obtained  from  dried 
samples,  those  on  pages  248  and  249  show  the  composition  of  natural 
(undried)  samples. 

IBON  ORES  (DRIED),  LAKE  SUPERIOR  DISTRICT. 


Gogebic 
Range. 

Mar- 

quette 
Range. 

Meno- 
minee 

Range. 

Mesaba 
Range. 

Vermilion 
Ran«re. 

Iron,  maximum,. 

64-15 

66-53 

60-28 

63-56 

65-00 

,,     minimum,  .         . 

48-16 

39-78 

37-60 

52-00 

59-20 

Phosphorus,  maximum, 

0-128 

0-415 

1-28 

0-11 

0-166 

,  ,          minimum, 

0-018 

0-012 

0-012 

0-023 

0-038 

Manganese,  maximum, 

6-95 

4-70 

4-60 

3-00 

0-25 

Silica,  maximum,        . 

23-80 

40-60 

41-53 

15-97 

9-28 

,,      minimum, 

2-57 

2-76 

4-33 

2-80 

4-77 

248 


APPENDIX. 


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APPENDIX. 


249 


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250  APPENDIX. 

American  Ore  Supplies. — As  already  mentioned,  the  American 
continent  is  rich  in  iron  ores.  The  extensive  deposits  in  the  Lake 
Superior  regions  contain  a  high  percentage  of  iron.  The  ores  are,  in 
many  places,  easily  quarried.  Much  ingenuity  has  been  displayed  in 
contriving  plant  for  digging  and  handling  the  ores.  The  chief  ore 
fields  are  far  from  the  fuel  deposits.  The  means  employed  for  trans- 
porting the  ores  are  ingenious  and  enterprising.  Steam  shovels  dig 
out  the  ore;  buckets  mounted  on  endless  bands  carry  the  ores  to 
vessels  or  to  railway  trucks  ;  capacious  steamers  which  can  take  in 
cargoes  of  12,000  tons  are  quickly  loaded,  and  convey  the  ore  over  the 
great  North  American  Lakes,  where  discharging  is  conducted  with  the 
utmost  despatch,  the  largest  vessels  being  emptied  in  the  course  of  five 
or  six  hours. 

It  is  not  unusual  to  transport  the  ore  a  distance  of  700  or  800  miles. 
At  Gary,  on  the  southern  shore  of  Lake  Michigan,  immense  iron  and 
steel  works  have  been  laid  out.  The  ore  for  these  works  is  taken 
direct  from  the  lake  steamers  to  the  storage  bins  or  heaps.  For  works 
in  and  around  Pittsburg  and  other  towns  it  is  necessary  to  convey  the 
ore  a  considerable  distance  by  train.  The  trucks  are  lifted  bodily  and 
the  contents  are  tipped  into  large  bins.  As  the  great  lakes  are  frozen 
during  the  winter  months,  enormous  heaps  of  ore  must  be  accumulated 
during  the  "open"  season  to  keep  the  furnaces  going. 


g  I 


APPENDIX. 


251 


Modern  Hoisting  Machinery.— A  modern,  well-equipped  American 
blast  furnace  working  on  rich  ore  requires,  on  an  average,  about  one 
ton  of  solid  material  at  the  top  every  minute.  Electrically-driven 
hoisting  machinery  has  been  set  up  for  dealing  with  this  quantity. 


On  the  opposite  page  is  an  illustration  of  a  modern  hoisting 
plant  by  the  Lilleshall  Company,  Limited,  Engineers,  Oakengates, 
Shropshire. 

The  following  abridged  description  of  the  plant  is  taken  from  The 
Iron  and  Coal  Trades  Review: — The  solids — ore,  fuel,  and  flux — are 
conveniently  tipped  from  railway  trucks  into  storage  bunkers.  From 
the  bunkers  the  solids  are  dropped  into  special  buckets  carried  on 
transporter  cars.  Each  bucket  has  a  capacity  of  6^  cubic  yards,  and 
can  be  closed  by  a  gas-tight  lid.  Through  the  centre  of  each  there  passes 
a  strong  shackle  extending  upwards  from  the  cone,  the  lower  part  of 


Fig.  97.— Demag  Transport  Car  with  two  Charging  Buckets. 


which  closes  the  bottom  opening  of  the  hopper.  Each  hopper  rests  on 
a  turntable  on  the  transporter  car.  The  turntables  are  revolved  by  an 
electric  motor  during  filling,  thus  securing  uniformity  of  loading  at  the 
storage  bunkers.  Each  turntable  is  mounted  on  a  separate  weighing 
machine  which  has  three  steelyards — for  ore,  fuel,  and  limestone 
weighings — and  each  steelyard  is  provided  with  a  poise  which  can  be 
locked  at  any  desired  position.  The  weighing  apparatus  is  also 
furnished  with  an  automatic  weight-recorder  which  prints  the  variations 
from  the  required  load.  Fig.  97  shows  the  transporter  car — which  is 
driven  by  a  22  horse-power  motor — for  conveying  the  buckets  from  the 
storage  bunkers  to  the  foot  of  the  blast  furnace  incline.  The  incline 
supports  a  travelling  trolly  which  is  moved  by  means  of  a  winding 


252 


APPENDIX. 


engine.  To  convey  the  weighed  charge  to  the  furnace  top  the  shackle 
of  a  loaded  bucket  is  connected  to  the  travelling  troll}',  the  winding 
engine  is  set  in  motion,  and  the  bucket,  with  its  contents,  is  lifted  from 
the  transporter  car  and  taken  evenly  up  the  track  until  it  arrives  at 
the  curved  part  of  the  upper  rail.  The  bucket  is  then  brought  to  rest 
on  the  seat  at  the  furnace  mouth.  A  gas-tight  joint  is  made  by  means 
of  an  asbestos  rope  which  is  carried  in  a  groove  in  the  seat.  Fig.  98 
shows  the  hopper  at  the  top,  and  the  illustration  on  the  opposite  page 
shows  a  view  of  the  plant.  The  bucket  cover  is  then  lowered  and  the 


Fig.  98.— Charging  Bucket  being  placed  in  position  at  top  of  Blast  Furnace. 

internal  cone  at  the  bottom  of  the  bucket  is  set  free,  while  at  the  same 
time  the  bell  of  the  furnace  is  automatically  lowered.  The  material 
drops  into  the  furnace  with,  it  may  be  mentioned,  the  minimum 
breakage  of  coke,  and  the  charge  is  evenly  distributed  in  the  furnace. 
As  the  top  of  the  hopper  is  closed  the  quantity  of  gas  escaping  is 
negligible. 

When  the  contents  of  the  bucket  have  been  discharged  the  bucket  is 
lifted  off  the  furnace.  Simultaneously  the  cover  is  lifted,  so  that  all  gas 
is  cleared  from  the  bucket  during  its  descent.  The  empty  bucket  is 
placed  on  the  transporter  car,  the  next  bucket  is  carried  upwards  and 
its  contents  are  charged  into  the  blast  furnace. 


LU 


APPENDIX  253 

Handling  Pig  Iron  at  Blast  Furnaces.— As  previously  stated, 

the  pig  iron  as  it  Hows  from  the  blast  furnace  may  be  run  into  moulds 
previously  prepared  in  the  sand  beds  in  front  of  the  furnace.  After 
the  pig  iron  has  solidified  it  may  be  lifted  by  hand  and  carried  to 
trucks.  This,  however,  involves  hard  labour  and  is  costly. 

For  more  quickly  dealing  with  the  pig  iron  produced,  pig-lifting 
and  pig-breaking  plant  is  employed.  When  the  pig  iron  has 
solidified,  each  sow  is  broken  off  from  the  runner,  and  a  sow  with  all 
its  pigs  attached — a  lot  known  as  a  "  comb" — is  taken  by  an  overhead 
crane  to  the  pig-breaking  machine. 

The  illustration  on  the  opposite  page  shows  a  "comb"  suspended 
from  the  electric  overhead  crane  at  the  Ayresome  Works,  near 
Middlesbrough.  This  handy  crane  was  erected  by  Messrs.  Babcock  & 
Wilcox,  Limited,  and  has  a  span  of  110  feet.  It  can  carry  a  load  of 
5  tons  at  the  rate  of  400  feet  per  minute. 

By  means  of  a  pig-breaking  machine — which  consists  essentially  of  a 
block  and  rams,  the  latter  worked  by  hydraulic  pressure — each  pig  in 
turn  is  held  down  and  broken  into  two  pieces,  and  the  sow  and  runner 
are  also  broken  into  pieces  of  suitable  size.  All  the  pieces  slide  down 
a  shoot  into  trucks  which  are  placed  in  position  to  receive  them. 

For  another  method,  the  pig  iron  as  it  is  tapped  from  the  blast 
furnace  is  collected  in  casting  ladles  and  conveyed  to  a  pig-easting 
machine.  Such  machines  consist  of  long  endless  metal  chains  which 
carry  a  continuous  series  of  iron  moulds  fixed  across  the  chains.  As 
the  chains  travel,  the  moulds  are  brought  in  succession  under  the  spout 
of  the  ladle  and  charged  with  fluid  pig  iron.  The  molten  metal  is 
quickly  cooled  by  water  which  is  sprayed  during  the  continuance  of 
the  travel.  By  the  time  a  filled  mould  has  reached  the  sprocket  the 
pig  iron,  in  the  form  of  cakes  about  21  inches  long,  10  inches  broad, 
and  only  f  inch  thick,  has  become  solid  enough  to  be  fit  for  dropping. 
Each  mould  is  inverted  as  it  rounds  the  sprocket,  and  as  a  consequence 
the  solidified  pig-iron  cakes  drop  into  a  trough  of  water,  from  which  it 
is  delivered  by  an  endless  belt  into  trucks.  While  the  moulds  are  still 
inverted  and  returning  to  the  pouring  or  filling  point,  they  are  sprayed 
with  lime-water.  The  heat  of  the  moulds  drives  off  the  water,  and  a 
protecting  coating  of  lime  is  left  on  the  moulds,  which  are  then  ready 
to  receive  another  lot  of  pig  iron  from  the  ladle. 

In  some  instances  the  pig  iron  is  tapped  from  the  blast  furnace  into 
a  ladle  and  taken  direct  to  a  converter  or  to  a  basic  open-hearth 
furnace.  But,  as  the  composition  of  the  pig  iron  in  a  blast  furnace  is 
subject  to  variation,  which,  of  course,  leads  to  irregularities  in  subse- 
quent working,  this  system  has  been  abandoned  in  several  works  and 
mixers  have  been  installed. 


254  APPENDIX 

MixePS  are  receptacles  in  which  pig  iron  is  stored.  They  have 
usually  a  capacity  of  about  300  tons,  but  much  larger  mixers  are  not 
uncommon.  All  the  pig  iron  from  the  blast  furnaces  in  a  work  may  be 
poured  into  the  mixer,  and  quantities  are  withdrawn  from  time  to  time 
as  required.  A  mixer  is  a  convenient  storing  receptacle ;  in  it  the 
composition  of  the  pig  iron  tends  to  become  averaged,  thereby  leading 
to  more  steady  working  of  steel-making  processes.  Modern  mixers 
resemble  tilting  open-hearth  furnaces  in  design.  8ome  mixers  have  gas 
producers  and  regenerators,  and  in  these  a  considerable  amount  of 
refining  is  sometimes  effected. 


APPENDIX.  255 

Movable  Furnaces.— In  the  Wellman  Rolling  Furnace,  the 
body,  which  is  roughly  rectangular  in  section,  is  enclosed  in  a  strong 
cage  constructed  of  steel  plates,  channels,  and  angle  bars,  with  stout 
tie-rods.  The  walls  and  roof  are  of  silica  bricks  and  a  suitable  lining 
is  put  in.  The  furnace  is  mounted  on  strong  steel  ribs  supported  on 
heavy  mocks. 

Rolling  is  effected  by  means  of  hydraulic  rams,  the  cylinders  of  which 
are  mounted  on  trunnions  at  their  lower  ends.  The  upper  ends  of  the 
piston-rods  are  attached  to  the  body  of  the  furnace.  To  move  the 
furnace  water  is  admitted  to  the  top  part  of  the  cylinder.  In  case  of 
accidental  failure  of  the  hydraulic  system  the  furnace  returns  to  its 
normal  position,  or  in  the  event  of  any  hitch  or  accident  occurring 
during  tapping  the  pouring  can  be  instantly  stopped. 

Slag  can  be  poured  off  at  any  time  during  the  working  of  a  charge, 
and  every  particle  of  metal  and  slag  can  be  removed  after  each  charge. 
A  movable  furnace  can  be  easily  brought  into  position  to  facilitate 
repairs. 

As  the  taphole  is  kept  above  the  level  of  the  charge  during  working, 
it  does  not  require  to  be  "made  up"  to  resist  the  pressure  of  the 
molten  charge,  but  is  only  loosety  covered  to  exclude  air.  It  is,  there- 
fore, easily  opened  as  soon  as  the  metal  is  in  correct  condition  for 
tapping.  This  is  particularly  advantageous  when  making  special  steels. 

Some  furnaces  are  provided  with  electric  (instead  of  hydraulic)  tilting 
gear.  A  photograph  of  such  a  furnace  is  reproduced  on  the  opposite 
page.  It  is  a  view  of  a  Wellman  rolling  furnace  built  at  Dommeldingen, 
Luxembourg,  by  Messrs.  Wellman,  Seaver  &  Head,  Limited,  and  shows 
the  furnace  in  its  ordinary  working  position  with  the  taphole  above 
the  level  of  the  charge.  The  electric  motor  is  also  shown,  as  well  as 
the  gearing  for  working  the  rack  and  pinion.  These  latter  are  enclosed 
in  metal  casing. 

The  regenerative  chambers  are  not  placed  under  the  furnace  as  in 
the  Siemens  design,  but  are  arranged  side  by  side  in  pairs  at  each  end 
of  the  furnace.  The  ports  are  mounted  on  flanged  wheels  and  can  be 
moved  away  from  the  furnace  ends  to  allow  the  furnace  to  be  tilted. 
This  is  clearly  shown  in  the  illustration  on  the  opposite  page,  and  in 
the  frontispiece.  When  pouring  is  finished  the  ports  are  again  moved 
towards  the  furnace  ends.  Movable  ports  permit  ready  access  for 
repairs. 

The  success  of  movable  furnaces  paved  the  way  for  the  introduction 
of  modified  steel-smelting  processes,  such  as  the  Talbot  and  the 
Bertrand-Thiel. 


256  APPENDIX. 

Charging*  Machines. — Open-hearth  furnaces  have  been  increased 
so  much  in  capacity  that  charging  machines  have  become  an  imperative 
necessity  for  dealing  with  the  heavy  tonnage  of  pig  iron  and  scrap  to 
be  charged. 

The  materials  to  be  charged  are  placed  in  long  narrow  charging  boxes, 
each  capable  of  containing  about  one  or  two  tons,  or  even  more. 
Charging  boxes  are  made  of  steel  plates,  one  end  consisting  of  a  steel 
casting  having  a  slide  and  an  opening  to  which  an  attachment  may  be 
made.  These  are  shown  on  the  right  lower  part  of  the  illustration  on 
the  opposite  page. 

The  charged  boxes  are  brought  within  the  range  of  the  arm  of  the 
machine.  The  arm  is  thrust  forward,  and  by  mechanical  movements  is 
locked  to  one  of  the  full  boxes.  This  is  borne  to  an  opened  door  of  the 
furnace,  is  pushed  in,  and,  by  a  rotary  motion  of  the  arm,  is  turned 
over.  By  these  movements  the  materials  in  the  box  are  dropped  in  the 
furnace.  The  box  is  then  withdrawn,  turned  into  its  former  position, 
and  deposited  on  the  trolly  from  which  it  was  taken.  Other  charged 
boxes  are  similarly  dealt  with,  so  that  a  furnace  is  quickly  charged. 

The  illustration  on  the  page  opposite  shows  an  overhead  charging 
machine  installed  by  Messrs.  Wellman,  Seaver  &  Head,  in  the  Parkhead 
Works,  Glasgow. 

Charging  by  hand  is  hot,  exhausting  work,  and  occupies  much  more 
time  than  machine  charging. 

A  50-ton  charge,  which  would  take  four  men  four  or  five  hours  to 
repair  and  charge,  may  be  charged  in  one  hour  by  a  charging  machine. 

Quick  charging  by  a  machine,  leads  to  larger  output  in  a  given  time, 
and  materially  reduces  costs  for  fuel. 

Originally,  charging  machines  were  worked  by  hydraulic  power,  they 
are  now  actuated  by  electricity.  Formerly  they  were  set  on  broad, 
gauge  rails  laid  parallel  with  the  range  of  furnaces,  and  the  boxes  were 
brought  on  a  narrow  gauge  railway  directly  in  front  of  the  furnaces. 
But  many  modern  machines  are  worked  on  the  overhead  system,  and 
as  the  arm  can  be  rotated  to  any  degree,  the  trolly  rails  may  be  run  in 
any  direction  near  the  furnaces.  Large  and  heavy  pieces  of  metal  are 
placed  on  a  fork  or  strong  peel,  and  can  then  be  charged  by  a  machine. 

In  the  illustration  facing  the  next  page  a  Wellman  overhead  charging 
machine  is  shown  in  the  act  of  conveying  a  box. 


• 


APPENDIX.  257 

The  applications  Of  electricity  to  the  various  branches  of  iron 
and  steel  manufacture  are  of  groat  importance.  Among  such  applications 
mention  may  be  made  of  the  following  : — 

I.  Separation   of    magnetic   (iron-containing)   portions  of    finely- 
crushed  ore  from  non-magnetic  portions  of  the  ore.     Some  ores  which 
are  too  poor  in  content  of  iron  may  be  successfully  treated  and  the 
richer  portion  profitably  made  into  briquettes  and  smelted. 

II.  Lifting  of  iron  and  steel  goods,  such  as  pig  iron,  plates,  rivets, 
etc.     This  is,  in  many  instances,  more  convenient  than  attaching  by 
hooks,  etc. 

III.  Driving  of  rolling  mills  and  other  kinds  of  machinery,  Bucb 
as  cranes.     Electric  power  is  cheaply  generated  from  blast-furnace 
gas,  and  is  used  for  driving  blowing  engines,  mills,  etc. 

IV.  Smelting  iron  ores.     Only  in  exceptional  circumstances — as,  for 
instance,  where  ores  are  cheap  or  of  superior  quality  and  suitable 
water    power  is  abundant — can   electric  smelting  be  economically 
carried  on. 

V.  Producing  special  alloys,  free  from  or  containing  only  traces  of 
carbon,  producing  high-grade  ferro-silicon,  etc. 

VI.  Refining  iron  and  steel. 

Owing  to  want  of  space  the  first  five  sections  cannot  be  dealt  with  in 
this  volume,  and  the  sixth  can  only  be  treated  in  outline. 

Electric  refining  furnaces  are  of  two  classes  — 

(a)  Arc  furnaces,  including  the  Girod,  Heroult,  Keller,  Nathusius, 
and  Stassano  furnaces.  In  these  the  high  temperature  is  derived  from 
the  electric  arc  between  the  electrodes,  the  heat  from  which  is  largely 
reflected  or  reverberated  from  the  furnace  roof. 

(6)  Induction  furnaces,  including  the  Grondal-Kjellin,  Frick,  and 
Rochling-Rodenhauser  furnaces.  In  these  the  high  temperature  is 
induced  by  the  resistance  to  the  current  while  passing  through  the 
metals  in  the  furnaces. 

For  refining  purposes  the  advantages  of  an  electric  furnace  over  an 
ordinary  fuel-fired  furnace  arises  from  the  rapidity  with  which  a  high 
temperature  can  be  attained  and  the  ease  and  constancy  with  which  it 
can  be  kept  up.  No  deleterious  element  (such  as  sulphur)  is  introduced 
by  the  heating  agent,  and  no  gases  (which  are  liable  to  be  occluded)  are 
introduced  during  the  refining.  Thus  a  pure  metal,  almost  free  from 
occluded  gases,  can  be  produced.  Overkilling  is  impossible. 

There  is  another  point  in  favour  of  electric  furnaces :  an  intense 
local  heat  can  be  produced— thereby  bringing  about  a  rapid  reaction 
between  the  metal  and  the  slag  which  acts  as  the  refining  oxygen 
carrier — at  points  far  from  the  walls  and  roof  of  the  furnace. 

In  shape  the  Grondal-Kjellin  furnace  may  be  said  to  be  like  a 
grindstone  laid  flat.  For  convenience  in  working  it  is  mounted  for 
tilting,  and  has  tapholes  at  different  levels.  It  is  constructed  of  highly - 
refractor}7  bricks  and  has  a  \\orking  lining  of  magncsite.  An  annular 
space  is  grooved  in  the  working  lining,  and  into  this  the  cold  or  the 
molten  metal,  as  the  case  may  be,  is  charged.  In  the  centre  of  the 

17 


258  APPENDIX. 

furnace  a  primary  coil  is  placed  :  the  metal  ring  in  the  annular  space 
constitutes  the  secondary  coil.  "An  alternating  electric  current  passing 
through  this  primary  coil  forms  an  induced  current  in  the  rin£  of  metal 
contained  in  the  hearth.  As  this  ring  forms  a  single  circuit  round  the 
core,  the  current  induced  in  it  is  approximately  equal  to  the  primary 
current  multiplied  by  the  number  of  turns  in  the  winding  of  the  coil. 
A  portion  of  the  charge  is  left  in  the  furnace  after  each 
tapping,  and  pig  and  scrap  are  added  to  this  in  proper  proportion,  so 
as  to  arrive  at  the  desired  carbon  content.  As  soon  as  the  metal  is 
properly  '  killed '  the  furnace  is  tilted  and  the  contents  tapped  into  a 
ladle.  .  .  .  The  upper  part  of  the  furnace  serves  as  a  charging 
platform,  and  the  necessary  materials  are  easily  charged  by  removing 
the  brick  covers." 

The  photograph  reproduced  on  the  opposite  page  shows  a  Grondal- 
Kjellin  furnace  at  Messrs.  Jessops'  Steel  Works,  Brightside,  Sheffield. 
This  furnace  is  provided  with  its  own  generator  set  and  control  gear. 
It  is  capable  of  carrying  a  charge  of  30  cwts.,  and  the  maximum  current 
consumed  is  250  kwa. 


°H      "S 


APPENDIX. 


CITY  AND  GUILDS  OF  LONDON  INSTITUTE. 


SYLLABUS— IRON  AND  STEEL  MANUFACTURE. 

The  Examinations  will  be  held  in  three  grades.  Candidates  will  be 
permitted  to  present  themselves  for  the  Examination  in  Grade  I.  in  a 
year  previous  or  subsequent  to  that  in  which  they  present  themselves 
for  examination  in  Grade  II.,  or  to  enter  for  both  Grade  I.  and  Grade 
II.  in  the  same  year.  No  Candidate  will,  however,  receive  a  Certificate 
until  he  shall  have  passed  the  Examinations  in  both  grades.  The 
successes  of  Candidates  in  either  grade  will  be  notified  to  the  Secretaries 
of  the  Centres  at  which  they  were  examined. 

Prizes  will  be  awarded  on  the  results  of  the  Examination  in  Grade 
II.  to  those  Candidates  only  who  have  passed  Grade  I.  in  a  previous 
year,  or  who  pass  both  parts  in  the  same  year. 

Candidates  for  the  Final  Examination  must  hold  a  Certificate  in 
Grade  II. 

In  order  to  encourage  Teachers  to  devote  special  attention  to  those 
processes  of  Iron  and  Steel  Manufacture  which  may  be  most  suitable 
for  their  respective  districts,  the  Syllabus  has  been  divided  into  two 
parts,  and  in  the  Examination  a  number  of  questions  will  be  given  so 
as  to  allow  considerable  choice  in  the  selection.  All  Candidates  will, 
however,  be  expected  to  afford  evidence  of  a  general  knowledge  of 
the  subject  as  a  whole,  and  in  order  to  pass  in  the  first  class  a 
Candidate  will  be  expected  to  answer  satisfactorily,  questions  both  in 
Iron  Manufacture  and  in  Steel  Manufacture.  In  the  Final  Examin- 
ation, Candidates  will  be  permitted  to  select  their  questions  either 
from  one  section  only  or  from  both. 

f.  GRADE  L 

Manufacture  of  Iron. 

1.  Composition  and  general  characters  of  the  chief  ores  of  iron. 

2.  Construction  and  mode  of  working  of  blast  furnaces. 

3.  Hot  and  cold  blast ;  effects  of  these  and  of  variations  in  amount 
of  fuel  and  flux  on  the  production  and  character  of  the  iron  made. 

4.  Physical  characters   of    pig   irons   from    various   classes   of  ore. 
Grey,  mottled,  and   white   irons.      Bessemer,  mine,  and  cinder  pigs. 
Numbering  of  irons. 

5.  Physical  characters   of  charcoal,  coal,  and   coke   used   for  iron 
smelting. 

6.  Chemical    and    physical    properties    of    iron    used   for  foundry 
purposes. 

7.  Chemical  and  physical  properties  of  forge  pigs. 

8.  Refining,  puddling,  and  the  production  of  finished  iron. 


XIV  APPENDIX. 

9.  Chemical  composition  of  fettling  and  of  wrought  iron. 

10.  A  general  knowledge  of  the  construction  of  furnaces,  hammers, 
and  rolls  required  for  the  manufacture  of  wrought  iron. 

11.  Manufacture  of  malleable  iron  castings  from  crucibles,  cupolas, 
or  the  open-hearth  furnace.     Practice  and  theory  of  ore  annealing. 


Manufacture  of  Steel. 

12.  Compositions  and  properties  of  the  materials  used  for  acid  and 
basic  linings  for  converters  and  steel  furnaces. 

13.  Outline  of  the  construction  of  cupolas,  converters,   and  of  the 
general  arrangement  of  a  Bessemer  plant. 

14.  Outline  of  the  construction  of  gas  producers,  melting  furnaces 
and  regenerators,  and  of  the  general  arrangement  of  an  open-hearth 
steel  plant. 

15.  Ingot  moulds,  nozzles,  and  stoppers ;   making  up  the  taphole, 
and  repairing  the  bed  of  the  open-hearth  furnace  between  heats. 

16.  Outline  of  the  reactions  involved  in  the  various  processes. 

17.  A  general  idea  of  reheating  furnaces,  soaking  pits,  hammers, 
and  rolls  used  for  converting  ingots  into  the  various  forms  of  steel 
required  for  the  market. 

18.  General  knowledge  of  the  furnaces  used  for  melting  in  crucibles 
by  means  of  coke  or  gas. 

19.  Chemical  and  physical  characteristics  of  coke  suitable  for  steel 
melting. 

20.  Composition  and  physical  characters  of   the  various  materials 
used  for  the  manufacture  of  crucible  steel — viz.,  Swedish,  Walloon,  and 
Lancashire  hearth  bars,  unconverted  and  cemented,  charcoal,  Swedish 
white  iron,  the  various  classes  of  steel  scrap,  and  ferro-manganese. 

21.  Hammering,  rolling,  and  reeling  of  crucible  steel. 

22.  Shear    and    double    shear    steel,   composition    and    method    of 
manufacture. 

23.  Testing  steel  in  tension,  with  arithmetical  calculations  connected 
therewith. 

GRADE  II. 

Manufacture  of  Iron. 

1.  Preparation  of  raw  ores  for   smelting ;  changes   in  composition 
thereby  produced. 

2.  Mechanical  preparation  of  iron  ores.     Magnetic  concentration. 

3.  Subsidiary  appliances  required  in  the  construction  and  working 
of  blast  furnaces — e.g.,  hoists,  blast  heating  stoves,  and  apparatus  for 
utilisation  of  surplus  gases. 

4.  Mechanical    charging    appliances.      Pig    casting    machines,    pig 
breakers,  and  similar  appliances. 

5.  Chemical  nature   of   fluxes   requisite   under  various   conditions. 
Composition  of  slags. 

6.  Handling  and  utilisation  of  blast-furnace  slags. 

7.  Chemical  composition  ol  charcoal,  coal,  and  coke  used  for  iron 
smelting.     Composition  of  gases  from  the  blast  furnace. 


APPENDIX.  XV 

8.  Chemical  and  mechanical  characteristics  of  pig  irons  from  various 
classes  of  ore. 

9.  Iron-founding,    including    cupolas,    moulds,   ladles,   and  foundry 
appliances. 

10.  Machine  moulding,  core  making,  foundry  sand  and  compositions. 

11.  Production  of  castings  of  special  kinds — e.g.,  large  castings,  fine 
castings,  chilled  castings,  &c. 

12.  The  theory  of  puddling.     Machine  puddling. 

13.  Mechanical  properties  of  the  various  qualities  of  wrought  iron. 
Composition  and  tests  of  wrought  iron  suitable  for  various  purposes. 

14.  Direct  production  of  wrought  iron. 

15.  Composition  of  iron  suitable  for  the  production  of  malleable 
castings.     Conditions  under  which  carbon  separates  from  white  iron. 
Other  changes  during  the  annealing  process. 

Manufacture  of  Steel. 

16.  Theory  of  the  acid  Bessemer  blow.     Theory  of  the  acid  open- 
"aearth  process.     Slags  produced. 

17.  Theory  of  the  basic  Bessemer  blow.     Theory  of  the  basic  open- 
nearth  process.     Slags  produced. 

18.  The  functions  of  manganese,  silicon,  and  aluminium.     Influence 
of  varying  quantities  of  silicon  and  manganese  on  the  temperature  of 
the  acid  Bessemer  blow. 

19.  Comparative  advantages  and  disadvantages  of  blowing   metal 
direct  from  the  blast  furnace,  and  re-melted  in  cupolas. 

20.  Chemical    and    physical    characteristics    of    coke    suitable    for 
Bessemer  cupolas  and  of  coal  for  gas  producers.       Composition  of 
producer  gases. 

21.  Bessemer,  open-hearth,  and  crucible  steel  castings.     Nature  and 
elimination  of  blowholes. 

22.  Low   pressure    surface    blown    modifications    of    the  Bessemer 
process  and  their  products. 

23.  Modified  open-hearth  processes  conducted  in  tilting  furnaces, 
&c. — e.g.,  the  Talbot  process,  the  "Rertrand-Thiel  process,  &c. 

24.  Methods  of  dealing  with   emergencies— «,</.,  hot  or  cold  heats 
or  blows. 

25.  Manufacture  and  compositions  of  clay  and  plumbago  crucibles. 
Annealing  clay  crucibles.     Stands  and  covers.     Sanding. 

26.  The  cementation  process.     Bar  numbers. 

27.  Impurities     eliminated    or     introduced    in    crucible    melting. 
Calculation  of  mixtures. 

28.  Causes  leading  to   "runners"   in    crucibles — e.g.,   inclusion   of 
basic  granules,  frost-crack,  &c. 

29.  Practice  of  hardening  and  tempering  steel. 


FINAL  EXAMINATION. 

Candidates  for  this  Examination  will  be  expected  to  answer 
questions  dealing  with  subjects  included  in  Grades  I.  and  II.,  and  may 
select  their  questions  from  one  section  only,  or  from  both.  The 
following  additional  subjects  will  also  be  included. 


XVI  APPENDIX. 

Manufacture  of  Iron. 

1.  Geographical  and  geological  distribution  of  iron  ores.     Relation 
of  composition  to  geological  distribution. 

2.  Handling  and  transportation  of  iron  ores  and  other  materials 
employed. 

3.  Thermal  calculations  relative  to  the  calorific  value  of  fuel  and  of 
blast-furnace  gases,  and  to  the  reactions  of  the  blast  furnace. 

4.  The  testing  of  cast  iron  otherwise  than  by  chemical  analysis. 

5.  Theories  of  puddling.     Calculations  relative  to  the  yield  of  pig 
iron  of  given  composition. 

6.  The  micro-structure  of  pure  iron,  of  wrought  iron,  and  of  various 
kinds  of  cast  iron. 

7.  The  production  of  spiegel-eisen,   ferro-manganese,  ferro-chrome, 
and  ferro-silicon,  in  the  blast  furnace.     Properties  of  these  alloys. 

8.  The  applications  of  electricity  in  the  production  of  iron  and  iron 
alloys. 

Manufacture  of  Sted. 

1.  The  relative  position  of  the  steel  trade  in  the  chief  steel-making 
countries,   and  the  reasons  for  the  adoption   of  certain  methods  or 
processes  in  particular  countries  or  districts. 

2.  The  general  arrangement  of  a  steel  works,  and  the  appliances  and 
methods  used  in  handling,  charging,  rolling,  pressing,  hammering,  or 
otherwise  shaping  large  masses  of  steel. 

3.  Chemical  and  thermal  calculations  relative  to  the  various  steel 
processes,  and  to  producer  gas. 

4.  Liquation  and  segregation  in  ingots.     Methods  of  producing  sound 
and  uniform  metal. 

5.  Influence  of  heat  treatment  of  steels  of  various  kinds.     Theory 
of  hardening,  tempering,  and  annealing. 

6.  Special  materials  used  in  steel  manufacture,  such  as  ferro-chrome. 
ferro-nickel,  tungsten,  &c.     Properties  of  the  special  steels  so  produced, 

7.  Influence  of    carbon  and    other  elements  on    the   tenacity  and 
ductility  of  the  various  qualities  of  steel.     Composition  necessary  to 
fulfil  given  mechanical  specifications. 

8.  Applications  of  electricity  in  the  production  of  steel. 


xvii 


INDEX. 


ACID,  26,  93. 

Bessemer  process,  58,  75. 
materials,  231,  232,  233. 
open  hearth,  60. 
pig  iron,  94. 

Siemens  process,  58,  60,  97. 
steel,  61. 

„      making,  97-126. 
,,  ,,        appliances, 

97-115,  254. 
Action  on  crucible,  48. 
Afterblow,  90. 
Aired  bars,  41. 
Air  chambers,  103. 

ior  Bessemer  process,  65. 
blastfurnace,  196. 
cupola,  154. 
hot-blast  stove,  200 
kilns,  185. 

Euddling,  17. 
iemens  process.  113. 
ports,  105,  255. 
preheated,  103,  107,  193. 
regenerators,  103,  106,  25,5. 
valves,  103,  107. 
Alloy,  4. 

Alumina,  26,  229,  230. 
Aluminium,  81,  134,  236. 
American  ores,  63, 247, 248, 249, 250. 
Analyses  of — 

American  ores,  248,  249. 
Anthracite,  226. 
Ayrshire  ore,  177. 

, ,        pig  iron,  240. 
Basic  pig  iron,  91,  94,  129,  213. 

„     slag,  95.    . 
Bauxite  brick,  245. 
Bessemer  pig  iron,  213. 

„         slag,  82,  95. 
Best  tap,  18. 
Bilbao  ores,  243. 
Blackband  ironstone,  177. 


Analyses  of — 
Blast-furnace  gases,' 221. 
,,  slags,  220. 

Blister  steel,  47. 
Blown  metal,  91. 
Boilings,  25. 
Bricks,  233,  245. 
Bridge-work  steel,  133. 
British  ores,  177. 
Brown  hematite  ore,  178,  243 
Bull  dog,  18. 
Calcined  ironstone,  183. 
Campanil  ore,  122,  243. 
Cannon  steel,  133. 
Cartagena  ore,  244. 
Castings,  iron,  162. 

,,         malleable,  169. 

steel,  166. 
Cast  steel,  47. 
Cemented  bars,  47. 
Charcoal,  226. 
Chrome  bricks,  245. 

,,       iron  ore,  245. 
Clay  band  ironstone,  177. 
Cleveland  ironstone,  177,  183. 

,,        pig  iron,  213,  240,  241, 
Coal,  226. 
Coke,  226. 
Core  sand,  148. 
Crucible  cast  steel,  47. 
Cumberland  ore,  178. 

,,  pig  iron,  240. 

Derbyshire  pig  iron,  240. 
Die  steel,  133. 
Dolomite,  85,  86. 
East  Coast  pig  iron,  240. 
Elba  ore,  244. 
Electrical  steel,  133. 
Ferric  ores,  178. 
Ferro-manganese,  80,  237. 
Ferro-silicon,  238. 
Ferrous  ores,  177. 
Fettling  materials,  18. 
Finishing  materials,  237. 


XV111 


INDEX. 


Analyses  of — 
Firebrick,  233. 
Fireclay,  233. 
Fire  sand,  148. 
Foreign  ores,  179. 
Forge  pig  iron,  12,  213,  241. 
Foundry  pig  iron,  162,  213,  241. 
Frodingham  ores,  205,  242. 
Ganister,  66,  233. 
Garrucha  ore,  244. 
Gases,  137,  221,  245,  246. 
Glengarnock  pig  iron,  239. 
Graphite,  234. 
Grey  pig  iron,  162. 
4Jun  steel,  133. 
Hammer  slag,  25. 
Hematite  ores,  178,  243. 

,,         pig  iron,  78,  91,  121, 

169,  213. 
Iron  castings,  162. 

„    ores,  122, 177, 178, 183,  205, 

242. 

Ironstones,  see  Ores. 
Lanarkshire  pig  iron,  240. 
Lancashire  pig  iron,  240. 
Lime,  85,  86. 
Limestone,  85,  86. 
Lincolnshire  ore,  205,  242. 
,,  pig  iron,  240. 

Magnesia  bricks,  245. 

,,         burnt,  85. 
Magnesite,  85,  86. 
Magnetic  ore,  178. 
Malleable  castings,  169. 

iron,  12,  47,  57,  146. 
Mediterranean  ores,  244. 
Medium  steels,  133. 
Melted  charge,  125. 
Mild  steel,  57, 78, 91, 125, 133,145. 
Monmouthshire  pig  iron,  240. 
Mottled  pig  iron,  241. 
Moulding  sands,  148. 
Northamptonshire  ore,  178. 

,,  pig  iron,  240. 

Nottinghamshire  pig  iron,  240. 
Occluded  gases,  137. 
Open-hearth  charge,  125. 
Ores,   122,   177,   178,    183,  205, 

242,  248,  249. 
Pig  irons,  12,47,78,91,94,121, 

129,   162,   169,  213,  239,  240, 

241,  243,  244. 
Plumbago,  234. 


Analyses  of — 

Pottery  mine,  242 

Producer  gas,  246. 

Projectile  steel,  133. 

Puddlers'  cinders,  25. 
,,        slags,  25. 

Purple  ore,  18. 

Rail  steel,  133. 

Red  hematite  ore,  178. 

Rubio  ore,  243. 

Sands,  U8,  233. 

Scotch  pig  iron,  241. 

Scrap  steel,  121. 

Ship's  plates,  133. 

Siemens  charge,  125. 
,,         slag,  126. 

Silica  brick,  233. 

Silico-ferro,  238. 

Silico-spiegel,  238. 

Slags,  25,  83,  95,  126,  220. 

Softeners,  238. 

Spanish  ores,  178,  243. 

Spathic  ore,  177,  243. 

Spiegel-eisen,  80,  237. 

Staffordshire  ores,  177,  242. 
,,  pig  iron,  240. 

Steel  castings,  166. 

Steels,  47, 57,  78, 91, 121,  125, 133. 

Stirlingshire  pig  iron,  240. 

Swedish  magnetite,  178. 
,,       pig  iron,  47,  213. 
,,       wrought  iron,  47. 

Tap  cinder,  25. 

Tinned  plates,  133. 

Tool  steel,  47,  50. 

Tyre  steel,  133. 

Vena  ore,  243. 

White  pig  iron,  241. 
„      sand,  233. 

Wood,  226. 

Wrought  iron,  12,  47,  57,  146. 

Yorkshire  pig  iron,  240. 
Annealed  steel,  52. 
Annealing  castings,  167. 
,,          furnace,  168. 
Anthracite,  204,  226.  227. 
Apatite,  177. 
Appliances,  see  Plant. 
Aolf  Ac2,  Ac3,  52. 
Arlt  Ar2,  Ar3,  52. 
Archimedian  screw,  101. 
Area,  Calculation  of,  144. 
Ash,  224,  225,  227. 


INDEX. 


XIX 


Ash,  Removal  of,  100,  101,  103. 
Ayrshire  ore,  177. 
,,         pig  iron,  177. 

B 

BABCOCK  &  WILCOX  Boiler,  221 

Ball.  Puddled,  22. 

Balling,  22. 

Ba  r  mill,  32,  33. 

Bars,  Aired,  41. 

,,     Blister,  40,  41. 

„     Cemented,  37,  47- 

„      Converted,  40. 

,,     Finished,  41. 

„     Flushed,  41. 

,,     Glazed,  41. 

,,     Merchant,  28. 

,,     Puddled,  28. 

„      Steel,  41. 

„     Swedish,  35. 

„      Tap,  39. 

„     Trial,  39. 
Bases,  26,  27,  61,  93. 
Basic  Bessemer  process,  89,  90,  91 . 

,,      bricks,  85,  86. 

,,     lining,  87,  88,89, 127j  128, 129. 

,,      machinery,  86,  87,  89,  128. 

,,     open-hearth  process,  127-132. 

,,     pig  iron,  91,  94,  129,  213. 

„     plant,  84,  85,  86,  87,  88,  127, 
128,  129. 

„     plug,  87,  88. 

„      press,  86. 

,,     process,  89,  90,  91,  130,  131. 

,,     refractory  materials,  233. 

„      Siemens  plant,  127,  128,  129. 

,,  „         process,  127-132. 

„     slag,  61,  95,  96,  131,  132. 

„     steel,  61,  166. 

,,     substances,  231. 

,,     tuyeres,  88. 
Bauxite  brick,  234,  245. 
Beehive  coke  oven,  228. 
Bell,  see  Cup  and  cone. 
Bessemer  air-blast,  65,  68. 

blowing  engine,  68. 
bottom,  Acid,  67. 
,,        Basic,  87,  88. 
„        Renewal,  64. 
converter,  Acid,  64,  76. 
Basic,  84,   85, 

86. 
crane,  70,  89. 


Bessemer  cupola,  71,  72,  74. 

,,         Heat    evolved     during 

blow,  81. 
ladle,  68. 
lining,  Acid,  66,  67. 

Basic,  84,  85,  86, 

127,  128. 

machinery,  68,  69,  70,  85, 
pig  iron,  213.  [89 

plant,  14-74,  84,  85. 
platform,  68. 
plug,  87. 
process,  58,  59,  75,  76,  77, 

89,  90,  91. 
pulpit,  68. 
scrap,  49. 
slag,  Acid,  82,  83. 
,,     Basic,  95,  96. 
steel,  61,  78,  166. 
Swedish  practice,  81. 
tuyeres,  Acid,  6(5,  67. 

Basic,  88. 
Best  best  iron,  28. 
„    tap,  17,  18. 
,,     Yorkshire  iron,  34. 
Bilbao  ores,  243. 
Binding  materials,  86,  114. 

,,        power,  150. 
Bituminous  coal,  23,  226. 
Blackbaud  ironstone,  177. 
Blast  for  converter,  65,  68. 
,,      ,,    cupola,  154,  155,  156. 
,,      ,,    furnace,  193. 
,,      ,,    producer,  98. 
,,     furnace,  188,  191. 
,,          ,,         blowing  engine,  196. 
,,  ,,         bosh,  190. 

,,  ,,        dimensions,  195. 

,,  ,,         equipment,  188. 

,,          ,,         foundations,  190. 

gases,  188,  210,  220, 

221,  222. 

,,  ,,         hearth,  190. 

,.  ,,         hoists,  201,251,252. 

lining,  188,  192. 
output,  195. 
slags,  188,  211,  212, 

220. 
,,  „         stack,  190. 

stoves,  196, 197, 198, 

199. 

tuyeres,  194,  195. 
well,  190. 


INDEX. 


Bleeding,  134. 

Blister  steel,  40,  47. 

Blooms,  28. 

Blow,  Bessemer  acid,  75,  76,  77. 

„  ,,         basic,  89,  90. 

Blower,  68,  69. 

„       Roots',  155,  156. 
Blowholes,  136,  165. 
Blowing  engines,  68,  196. 
Blown  metal,  91. 
Blows,  Cold,  82. 
„       Hot,  82. 
Blue  Billy,  176. 
Boiling,  21,  22,  25,  122. 
Boilings,  25. 
Bosh,  195. 

Bottom,  88,  108,  128. 
Boxes,  37,  167,  168,  169,  171. 
Breeze  fire,  53. 
Bricks,  Basic,  85,  86. 

Bauxite,  234,  245. 

,,       Chrome,  234,  245. 

,,      Dolomite,  233. 

„       Fire-,  231,  232,  233. 

„       Ganister,  232. 

,,       Magnesia,  233,  245. 
Neutral,  129. 

„      Silica,  232,  233. 
Brinell's  formulae,  52. 
Briquettes,  182. 
British  ores,  177. 

Brown  hematite  ore,  176,  178,  243. 
Buckstave,  103,  107. 
Bulldog,  17,  18. 
Burden,  203. 

Self-fluxing,  205. 
Burning  in,  128. 
out,  12. 
Burnt  dolomite,  85. 

„      iron,  8. 

,,      limestone,  85,  89. 

,,      magnesite,  85. 

,,      pyrites,  176. 
Bustle  pipe,  207. 


CALCIC  phosphate,  93. 
Calcination  of  ores,  182,  183,  184. 
Calcined  ironstone,  183. 
Calorific  power,  226. 
Campanil  ore,  122,  243. 
Candles,  Puddlers',  22. 


Carbon,  5,  6,  145,  146. 
addition,  194. 
Cement,  52. 
Combined,  12. 
deposition,  228. 
dioxide,  5,  26,  97. 
Fixed,  225,  226. 
Graphitic,  12. 
Hardening,  52. 
impregnation,  210. 
penetration,  39. 
Carbonic  acid,  26. 
3arburisation,  40. 
Cartagena  ore,  244. 
Case  hardening,  171. 
Cast  ng  pit,  69,  110. 
^ast  ngs,  Annealing,  167 
Chilled,  163. 
Cleaning,  167. 
Dry  sand,  150. 
Green  sand,  150. 
Iron,  148,  162. 
Malleable,  169. 
Steel,  148,  165,  166. 
Cast  iron,  147. 

castings,  163,  164,  16& 
cylinders,  163,  164. 
Hardened,  162,  163. 
Shrinkage  of,  165. 
Softened,  162. 
tests,  147. 
steel,  35,  42,  47. 
Cementation  boxes,  35,  38. 
,,  cover,  39. 

,,  furnace,  37. 

„  pots,  35,  38. 

,,  process,  35. 

Cement  carbon,  52. 
Cemented  bars,  37,  47. 
Chamber,  Regenerative,  103. 
Changes  induced  in  steel,  51. 
Charcoal,  204,  226,  228. 
Charger,  45. 

Charges,  19,  38,  39,  45,  71,  73,  76, 

77,  89,  124, 125, 130, 156, 167,203. 

Charging,  Appliances  for,  115,  116, 

251,  256.  [252. 

„         blast  furnaces,  207,  251, 

boxes,  38,  39,  167. 
„        converters,  76,  77. 
„        crucibles,  45. 
„        cupolas,  71,  73,  156. 
„        ingots  into  furnace,  138, 
139. 


INDEX. 


XXI 


Charging  kilns,  185,  186. 

, ,      lime  into  furnace,  89. 

,,      Machinery  for,  11 5, 25 1,256. 

„      reheating  furnaces,  188. 

„      soaking  furnaces,  141. 
Checkers,  107. 
Checker  work,  103,  199. 
Chemical  change,  4. 

,,         combination,  6. 

,,         composition, see  Analyses, 

,,         formulae,  5,  6. 

„  reactions,  5,  6,  27,  28,  79, 
80,  92,  93,  122, 183, 209, 
210,  211. 

,,         residuals,  103. 

,,        symbols,  3,  5,  7. 
Chemical  considerations — 
Acid  Bessemer  process,  78,  79. 

,,     Siemens  process,  122,  123. 

Basic  Bessemer  process,  91,  92, 
qq 

t/O. 

,,      Siemens  process,  131. 
Blast-furnace  working,  209,  210, 

211. 

Crucible  process,  47,  48,  49. 
Malleable  castings  process,  169. 
Puddling  process,  25,  26,  27,  28. 
Chilled  castings,  163. 
Chimney,  16,  105. 
Chrome  bricks,  234,  245. 

iron  ore,  85,  129,  233,  245. 
Chromic  oxide,  230. 
Cinder,  see  also  Slag. 

Elimination  of,  23,  26. 
Flue,  177. 
Functions  of,  27. 
hole,  17. 
notch,  17. 
pig  iron,  177. 
Puddlers',  177. 
Tap,  24,  25. 
Truck,  23. 
Utilisation  of,  129. 
waggon,  23. 
Clay,  4,  229,  232. 
Clay  band  ironstone,  177. 
Cleaning  castings,  167. 
Clearing  stage,  20,  21. 
Cleveland  ironstone,  183. 

pig  iron,  131,  213,  240, 

241. 

Clinker,  39. 
Coal,  39,  97,  204,  226,  227. 


Coarse  grained  steel,  52,  53. 
Coke,  156,  204,  225,  226,  227,  228. 

,,      ovens,  228. 

Coking,  227,  228. 

coal,  227. 

Cold-shortness,  8,  57,  84. 
Composition,  see  Analyses. 
Compounds,  4. 
Compound  slag,  228. 
Cone,  99,  186,  192,  193. 
Contraction  of  area,  145. 

, ,  Calculation  of, 

145. 

Conversion,  40. 
Converter,  64,  166. 

bottom,  67,  87,  88. 
hood,  67,  87. 
lining,  66. 
nose,  67,  87. 
plug,  67,  88. 
rack,  65. 
ram,  65. 
ramming,  67. 
renewal,  64. 
trunnion,  65. 
Cooling,  52. 
Cores,  149. 
Core  sand,  148. 
Cotter  bolts,  89. 
Country  heat,  40,  41. 
Cowper  stove,  197. 
Crab,  115. 

Cranes,  70,  111,  115. 
Critical  points,  51. 
Crocodile  squeezer,  28. 
Crucible  cast  steel,  35,  42,  47,  49, 

50,  51,  55. 
„         charge,  46. 
Crucibles,    42,    45,    49,    150,    166, 

167. 

,,          Action  on,  46. 
Crushing  strength,  161. 
Crystallisation,  11,  163. 
Cumberland  ore,  175,  178. 
, ,  pig  iron,  240. 

Cup  and  cone,  192,  203,  204. 
Cupola,  71,  72.  150,  153,  155. 

,,  '      Bessemer    works,    71,    72, 

73,  74. 
,,       charge,  156. 

Drop  bottom,  152,  153. 
„        Foundry,  150. 
,,       Fuel  for,  156. 


IHDBX. 


Cupola  receiver,  154. 

Solid  bottom,  151,  153. 
„      Steel  works,  71,  72,  73. 
Currents  in  blast  furnace,  206,  207. 
Cutlery,  49. 
Cutting  edge,  < 
Cyanides,  210. 
Cylinders,  163,  164,  192. 


49. 


DAMPER,  16,  107. 

Dannemora  bar  iron,  35. 

Decarburising,  117. 

Defects  produced  by  hardening,  54. 

Deoxidising,  13,  77,  79,  93,  119. 

„  materials,  235. 

Dephosphorising,  27,  84. 
Derbyshire  pig  iron,  240. 
Diminishing  weight  of  charges,  4b. 
Direct  process,  11. 
Distorted  roof ,  113. 
Dogs  for  lifting  ingots,  77,  135. 
Dolomite,  85,  86,  128,  233. 

bricks,  233. 
„        lining,   85,   86,  87,  128 

Double  shear  steel,  41. 
Doubling,  23. 
Downcorner,  207. 
Downtake,  207. 
Draught,  45,  107,  226. 
Drawing  wire,  9. 
Drop  of  flame,  78. 
Dry  puddling,  11. 

,,    sand  castings,  150. 
Ductility,  9. 
Duff  producer,  102,  103. 
Durham  coke,  179. 
Dust  catcher,  191. 

„    pocket,  107. 


EAST  Coast  pig  iron,  240. 
Elasticity,  9. 

,,         Limit  of,  9. 
Elba  ore,  244. 
Electric  furnaces,  257,  258. 
Elements,  4. 
Eliminate,  12. 


Elimination,   25,   27,    61,    90,  91, 
92. 

Elongation,  9,  144. 

Engine,  Travelling,  111. 

Equivalents,  6,  7. 

Explosion,  113. 

Expulsion  of  slag,  23. 

Extensibility,  9. 
Extraction,  3. 


FERRIC  ores,  178. 

,,       oxide,  5,  6,  230. 
Ferro-manganese,  49,  80,  235,  237. 
Use  of,  49,  119, 

123,  129. 
Ferro-silicon,  236,  238. 
Ferrous  carbonate,  230. 
-ferric  ores,  177. 
ores,  177. 

oxide,  4,  6,  26,  229,  230. 
silicate,  10. 
Fettling,  12,  13,  14,  17,  18. 
Functions  of,  27. 
materials,  18. 
Fibrous  structure,  11. 
Fiery  steel,  134. 
Fillers,  207. 

Fine-grained  steel,  52,  53. 
Finishing  materials,  237. 
Fire-bars,  41. 

-bridge,  16,  17. 
-grate,  17,  38. 
-hole,  17. 
-sand,  148. 
,     -stones,  232. 
Firebrick,  231,  232,  233. 

stoves,  200. 
Fireclay,  232,  233. 
nozzle,  68. 
sleeve,  68. 
,,         stopper,  68. 
Firth's  Steel  Works,  104. 
Flame  drops,  78. 

„      flue,  197,  207. 
Flue,  15,  44. 
„     -bridge,  16,  17. 
,,     cinder,  176. 
Fluid  metal,  71. 
Fluorspar,  130,  132,  230. 


INDRX. 


xxiii 


Flushed  bars,  41. 

Fluxes,  4,  21,  24,   118,    188,  204, 

205,  228. 
Fluxing,  11. 

,,       oxide,  12. 
Foreign  ores,  179. 
Foreplate,  17,  110. 
Forge  pig  iron,  12,  213,  241. 
„      plant,  28. 
„      train,  31,  32. 
Formulae,  4,  5. 
Foster's  tuyeres,  195. 
Foundry  cupola,  150,  151,  152,  153. 
,,       Drop  bottom,  153. 
,,       receiver,  154. 
,,       Solid  bottom,  153. 
ladle,  157,  158,  159. 
mixtures,  160. 
pig  iron,    160,    162,   213, 

241. 

,,         practice,  148. 
Fracture,  40. 

,,         of  ingot,  46. 
Frit,  113. 

Frodingham  ores,  205,  242. 
Fuel,  3,  7,  188,  224. 
„      for  annealing  furnace,  169. 
„       ,,  Bessemer  process,  82,  91, 

95. 

„       „  blast  furnace,  204,  215. 
,,  calcining  kiln,  186,  187. 
,,       ,,  cementation  furnace,  39. 
,,       ,,  crucible  furnace,  44. 
,,       ,,   cupola,  156. 

„   gas  producer,  97,  246. 
,,       ,,   open-hearth  furnace,  97. 
,,       ,,  puddling  furnace,  23. 
,,       ,,  regenerative  furnace,  97. 
„       ,,  reheating  furnace,  138. 
,,       ,,  reverberatory  furnace,  14, 

23. 

,,       ,,  Siemens  furnace,  97. 
,,       ,,  soaking  furnace,  140. 
,,     Natural,  226. 
,,     Prepared,  226. 
Funnel,  45. 

Furnace,  Annealing,  168. 
Blast,  188. 
Cementation,  37. 
Crucible,  42. 
Electrical,  257 
Movable,  103,  255. 
Open-hearth,  103,  255. 


Furnace,  Puddling,  14. 

Regenerative,  103,  255. 
Reheating,  138. 
Reverberatory,  14. 
Rolling,  103,  255. 
Siemens,  103,  255. 
Soaking,  138. 
Tilting,  103. 
Vertical,  140. 


GANGUE,  4,  174,  219,  228. 
Self-fluxing,  219. 
Ganister,  66,  232,  233. 

brick,  232. 

,,         lining  of  Bessemer  con- 
verter, 67. 
Garrucha  ore,  244. 
Gas  engine,  221. 

Natural,  9*7,  246. 
ports,  105. 

producers,  97-103,  141,  246. 
A.  B.  Duff,  102. 
,,         Siemens,  98. 
Wilson's,  98. 
,,  ,,        self  clean- 

ing, 101. 
valve,  103. 
Cases  from  blast  furnace,  188,  210, 

220,  221. 

,,     producer,  246. 
„     steel,  137. 
Occluded,  136,  137,  257. 
Reducing,  137,  220. 
Surplus,  220,  221. 
Utilisation  of,  221,  222,  223. 
Waste,  220. 
German  Steel  Trade,  63. 
Gjers'  kiln,  186,  187. 

„     soaking  pit,  138,  139. 
Glazed  bars,  41. 
Glengarnock  pig  iron.  239. 
Goose-neck,  194. 
Grading  pig  iron,  214,  217. 
Graphite,  12,  234. 
Graphitic  carbon,  12. 
Grate-bars,  17. 
Green  sand,  150. 
Grey  pig  iron,  162,  216,  217. 
Guide  mill,  32,  33. 


XXIV 


INDEX. 


H 


HAMMER  scale,  24. 
slag,  25. 

Hardening  carbon,  52. 
„         defects,  54. 
,,          iron,  163. 
„         steel,  51,  52,  54. 
Hard  tap,  115. 
Head  melter,  45. 
Hearth,  Blast-furnace,  190. 
Heat,  Country,  42. 

Double  shear,  42. 
evolved,  81. 
Irish,  42. 
Melting,  42. 
Single  shear,  42. 
Spring,  41. 
Steel-through,  42. 
units,  225. 
value,  225,  226. 
Helve,  29. 
Hematite  ores,   18,  167,  175,  176, 

178,  243. 
pig  iron,    78,    91,    121, 

169,  213. 

Hoists,  201,  251.  252. 
Hole,  Cinder,  17. 
„     Firing,  17. 
„     Staff,  17. 
,,     Steel-melting,  42. 
,,     Stopper,  17. 
Holley's  improvement  on  converter, 

64. 

Homogeneous  steel,  42. 
Honeycombed  steel,  47,  119. 
Hopper,  99. 
Horse-shoe  main,  194. 
Hot-blast,  193. 

,,  main,  193. 
„  stove,  196. 
„  „  Cast  iron,  196. 

„  ,,      Firebrick,  196. 

,,  ,,      valve,  199. 

,,  ,,      Working  of,  200. 

,,          tuyeres,  194. 
House,  Steel-melting,  42,  43. 
Housings,  31,  32,  34. 
Hungry  pigs,  13. 
Hydrocarbons,  97,  224,  226,   226 

227. 
Hydrogen,  7,  97. 


IMPACT,  142. 
Imported  ores,  179. 
Impurities,  8,  135,  231. 
Increased  yield,  13,  24,  40. 
Inferior  steel,  46. 
Ingot,  Bessemer,  77. 

,,      Bleeding,  134. 

„      Contraction  of,  135. 

„      Cooling  of,  134,  135. 

„      Impurities  in,  135. 

,,      iron,  57. 

„      moulds,  70,  134. 

„  „        Stripping,  70. 

„      Objectionable,  134. 

,,      outer  crust,  134. 

,,      Perfect,  136. 

,,      Pressing,  136. 

,,      Removal  of,  135. 

,,      Scorched,  46. 

,,      Segregation  in,  135. 

„      Shrinking  of,  J  34. 

,,      Solidified,  134,  135. 

,,      Sound,  134. 

,,      Stoppering,  134. 

„      Stripping,  70,  71,  77,   120, 

,,      Treatment  of,  137. 
,,      unsound  tops,  135,  136. 
Injector,  17,  99,  100. 
Irish  ores,  176. 

„    temper,  41. 
Iron,  Best  best,  28. 

Best  Yorkshire,  34. 

Burnt,  8. 

castings,  148,  162,  163,  164. 

Chemically  pure,  4. 

Dannemora,  35. 
,,     Extraction  of,  3. 
,,     Ingot,  57. 
„        ,,      moulds,  70. 
„        ,,  ,,        Cooling  of,  135. 

,,     Malleable,  11. 
„     ores,  122,  177,  178,  183,  205, 

242. 

„     oxides,  4,  5,  6,  26,  229,  230. 
,,     Properties  of,  8,  11. 
„     Pure,  4,  8. 
„     pyrites,  230. 
„     Reheating,  137. 
„     rust,  4. 


INDEX. 


XXV 


Iron,  Spongy,  22. 
Swedish,  35. 
Treble  best,  28. 
Wrought,  11,  12,  47,  57,  146, 

147. 

Slag  in,  11. 
Yorkshire,  34. 


JUMBO,  175. 


K 


KIDNEY  ore,  175. 
Killing,  46. 
Kiln,  Calcining,  185. 
„      Gjers',  186. 
„     Scotch,  185. 
Kindling  furnace,  113. 
,,        producer,  100. 
,,         Siemens  furnace,  107. 
Kish,  162. 


LADLE,  Bessemer,  68,  111,  112. 
„       Crane,  89. 
,,       for  hot  metal,  73. 
„        ,,  side  tapping,  89,  90. 
Ladles,  Foundry,  157. 
Geared,  158. 
Mounted,  159,  160, 
Lanarkshire  pig  iron,  240. 
Lancashire  hearth,  35. 

ore,  175,  179. 
,,          pig  iron,  240. 
Launder,  110 
Lignite,  204. 
Lilleshall  Company,  111. 
Lime,  26,  85,  228,  229,  230. 
,,      in  blast  furnace,  215. 
Limestone,  85,  86. 
Lincolnshire  ores,  205,  242. 
,,  pig  iron,  240. 

Lining  converter,  Acid,  67,  86,  87, 

88. 

„  „      Basic,  86. 

„      Siemens  furnace,  114,  127, 

128. 
„      with  dolomite,  128. 


Lining  with  ganister,  66,  67. 

,,        ,,     magnesia,  128. 
Lloyds'  tuyere,  194. 
Loam,  114,  231. 
Loss  of  metal,  74. 
Lower  oxide,  80. 


MACHINE  charging,  115,  202,  256, 
Magnesia,  26,  85,  230. 

bricks,  233,  245. 
,,         limestone,  85,  86. 
,,         lining,  128. 
Magnesite,  85,  86,  128. 

,,          bricks,     see     Magnesia 

bricks. 

Magnetic  concentration,  182. 
,,         ore,  178. 
,,         oxide,  5. 

Making  up  taphole,  114,  115. 
Malleable  castings,  167,  168,  169. 
,,         iron  (wrought  iron),  11, 

12,  47,  57,  146,  147. 
Malleability,  9. 
Manganese,  7,  9. 

Action  of,  48,  49,  79, 
80,81,93,94,95,119, 
120,  121,  129,  214. 
ores,  179,  181. 
,,  silicate,  48. 

Manganous  oxide,  26,  28. 
Manhole,  38. 
Marsh  gas,  221. 
Martin  process,  60. 
Mechanical  testing,  142. 
Mediterranean  ores,  244. 
j  Medium  steel,  119,  133. 
Melted  charge,  125. 
Melting-down  stage,  19,  122. 
,,        heat,  40. 
,,        of  metal,  150. 
,,  slag,  228. 
,,  steel,  42. 
Merchant  bar,  28. 
Mercury,  Quenching  in,  54. 
Metal,  Fluid,  71. 
,,       mixer,  71. 

Solidifying,  82. 
„       Wild,  82. 
Metallic  state,  3. 
Metalloids,  7. 


XXVI 


INDEX. 


Methane  gaa,  97. 

Mild  steel,  57,  58,  91,   119,    125, 

133,  145. 

,,  specifications,  146. 

Mill,  32,  33. 
„     Bar,  32,  33. 
,,     Guide,  32,  33. 
„    Merchant,  32,  33. 
,,     train,  28. 
Mixer,  71. 

Monmouthshire  pig  iron,  240. 
Mottled  pig  iron,  216,  241. 
Moulding  cores,  149. 

,,        materials,  149,  166. 

sands,  148. 
Moulds,  45. 

,,        for  castings,  148. 
,,        for  crucibles,  45. 

Ingot,  70. 
,,       Loam,  150. 
Reeked,  46. 

Movable  furnace,  103,  255. 
Muffles,  53. 
Mushet  steel,  40. 

N 

NATIVE,  174. 
Natural  gas,  97,  246. 
Neutral  course,  128. 

,,       refractory  materials,  234. 

,,        substances,  234. 
Non-metal,  4,  7. 
Normal  steel,  52. 
Northamptonshire  ore,  178. 

,,  pig  iron,  240. 

Nostrums,  49. 
Notch,  17. 

Nottinghamshire  pig  iron,  200. 
Nozzle  of  ladle,  68,  70. 


OCCLUDED  gases,  136, 137,  165,  257. 
Occlusion,  136,  165. 
Oil-hardened  tools,  56. 
Open  hearth,  166  (see  Siemens). 
Ores,  Aluminous,  176. 

,,     American,  247,  248,  249,  250. 

,,     Antrim,  176. 

,,     Ayrshire,  177. 

„     Belfast,  176. 


Ores,  Bilbao,  243. 

Blackband,  175,  177,  179. 
Brown    hematite,    175,    176, 

178,  243. 

Campanil,  121,  122,  243. 
Cartagena,  244. 
Clayband,  177. 
Cleveland,  175, 177,  179,  183. 
Cumberland,  175,  178. 
Dunderland,  179. 
Elba,  179. 
Ferric,  175. 
Ferrous,  175. 
Ferrous-ferric,  175,  176. 
Foreign,  179. 
Franklinite,  175. 
Frodingham,  205. 
Garrucha,  244. 
Greek,  179. 
hematite,   Brown,    175,    176, 

178,  243. 

„          Red,  167, 175, 178. 
Ilmenite,  175. 
Imported,  179. 
Indian,  179. 
Irish,  176. 
Kidney,  175. 
Lancashire,  175. 
Lenticular,  176. 
Lincolnshire,  205,  242. 
Magnetite,  175,  176,  178. 
Manganese,  179. 
Mediterranean,  179. 
Northamptonshire,  178. 
Norwegian,  179. 
Pencil,  175. 
Pottery  mine,  242. 
Purple,  17,  18,  176. 
Red  hematite,  167,  175,  178. 
Rubio,  243. 
Russian,  179. 
Self -fluxing,  205. 

„    -going,  205. 
Siderite,  175. 
Spanish,  178,  179,  243. 
Spathic,  175,  177,  243. 
Specular,  176. 
Staffordshire,  177,  242. 
,,     Swedish,  178. 
Osborn's  Works,  109. 
Ovens,  Coke,  228. 
Oxidation,  12,  74,  78,  79,  117,  130. 
„         tints,  56. 


INDFX. 


XXV11 


Oxygen,  3. 

,,        carrier,  25. 


PACK  INC.  pots,  39. 
Pattern,  lt>7. 
Peat,  204. 
Peel,  116. 
Pencil  ore,  175. 
Penetration  of  carbon,  39. 
Permanent  set,  10. 
Phenomenon  of  hardening,  51. 
Phosphoric  acid   '26. 

anhydride,  26. 
Phosphorus,  Elimination  of,  26,  27, 

90,  127. 
„  in  pig  iron,  8,  161,  177, 

1 80. 

,,          in  steel,  8. 
Physic,  45,  49,  80. 
Pig  bed,  207. 

,,    boiling,  1 1. 
Pigging  back,  124. 
Pig  iron,  188,  213. 

,,       Abnormal,  217. 

,,       Acid  Bessemer,  94,  181, 
213. 

,,          ,,       Siemens,  181. 

„       All-mine,  181. 

,,       Basic  Bessemer,  94,  181. 
213. 

,,       Carbon  in,  214. 

„       Chilled,  217. 

„       Cinder,  117,217,218. 

„       Cleveland,  213. 

„       Forge,  12,  213. 

„       Foundry,  160,  161,  180. 

„       fractures,  118,  216,  217. 

„       Grading  of,  217. 

„       Grey,  216,  217. 

„       Malleable  castings,  169. 

„       Manganese  in,  94,  95,  2 1 5. 

„       Mottled,  216,  217,  219. 

,,        Phosphoric,  132. 

,,       Phosphorus  in,  214. 

„       Production  of,  180,  181. 

„       Puddling,  12. 

„        Silicon  in,  214,  215. 

„        Silvery,  219. 

„       Soft,  219. 

„       Sulphur  in,  214. 


Pig  iron,  Swedish,  35,  48,  181,  213. 

White,  216,  217,  219. 
Piles  for  reheating,  28,  42. 
Pipe,  136. 

,,      stove,  196. 
Piping,  136. 
Pistol  pipe  stove,  197. 
Plant  for  blast  furnace,  188. 

Bessemer,  64-74,  84-89. 
,,         open     hearth,     97  -  115, 

127-129. 

,,         Siemens,  97. 
Platform,  68,  69. 
Plating,  41. 
Plumbago,  234. 

,,          crucible,  49. 
Plug,  87,  88. 
Plunger,  192. 
Points,  Arrestment,  51. 

Critical,  51. 

Pon  sity  of  moulds,  150,  166. 
Potash,  200. 
Pots,  42,  105,  167,  168. 
,,     Cementation,  38. 
Pottery  mine,  18,  129,  242. 
Pouring  metals,  76. 
Preheated  air,  103,  107,  196. 
Problem   of   elimination  of   phos- 
phorus, 61,  63. 

Producer  gas,  97,  103,  141,  246. 
Producers,  Gas,  97-103,  140. 
Properties  of  iron,  8. 
Protection  of  piles,  42. 
Puddled  ball,  22,  28. 
„       bars,  23,  28. 
,,       steel,  49. 
Puddlers'  candles,  22. 

,,         cinders,  25,  177. 
„         slags,  25,  177. 

tap,  177. 
Puddling,  Dry,  11. 

,,         furnace,  14-17. 

,,  ,,         Preparation  of, 

18. 
„         process,  19. 

balling,  22. 
boiling,  21. 
charging,  19. 
clearing,  20. 
coming         to 

nature,  23. 
melting     down, 
19,  20. 
18 


XXV111 


INDEX. 


Puddling  process,  rabbling,  12,21. 
,,  ,,       shingling,  23. 

Wet,  11. 

"Puller  out, "45. 
Pulpit,  68. 
Pulpit  man,  68. 
Purifying  melted  pig  iron,  64. 
Purple  ore,  17,  18,  129,  17G. 
Pyrites,  230. 
Pyrometer,  53. 


QUARTZ,  7. 
Quenching  in  brine,  54. 

,,  mercury,  54. 

oil,  54. 

„  water,  51,  53   54. 

Quick -cutting  tool  steel,  50. 


RABBLING,  12,  21. 
Ramming,  67,  87,  128. 
Rapid-cutting  tool  steel,  49,  50. 
Reactions,  5,  6,  27,  28,  48,  79,  80, 

Ji2,  93,  123,  209,  210. 
Recarburising,  81,  93. 

,,  materials,  235. 

Receiver,  154. 
Red  hematite  ore,  167,   175,    176, 

178. 

Red-shortness,  8.  57. 
Reducing  gases,  137,  221. 
Reduction,  3,  13,  209,  210. 
Reeking,  46. 
Reeling,  47. 
Refining,  7. 

Refractory  materials,  230,  231. 
Acid,  232. 
Basic,  233. 
Neutral,  233, 

234. 
Regenerative  chambers.    103,   105, 

141,  255. 

,,  system,  103,  107. 

Regenerators,  103,  105. 
Reheating  ingots,  47,  77,  137. 

piles,  28,  42. 
Remelting  pig  iron,  1 63. 
Repairing  sand  bottom,  1 15. 


Kephosphorising,  91. 
Residuals,  103. 
Retardation,  51,  52. 
Retort  ovens,  228. 
Rcverberatory  furnace,  i4, 138,  150 
Rolling  furnace,  103,  265. 
Rolls,  Forge,  23. 
Roots'  blower,  In5. 
Rubio  ore,  243. 
Rust,  4. 


SAND,  7. 

„      Belgian,  114,  232. 
Core,  148. 
Dry,  150. 
Fire,  148,  149. 
for  pig  moulds,  209. 
Fritting,  113. 
Green,  150. 
Lining,  114. 
Moulding,  148,  149. 
Silver,  114,  232. 
White  Be' gian,  114,  233. 
Saggers,  167. 
Sap,  40,  41. 
Scotch  kilns,  185,  186. 
„       pig  iron,  241. 
,,       tuyeres,  194. 
Scrap  steel,  121. 
Segregation,  135. 
Selective  action,  12,  78. 
Self-fluxing  ore,  205. 

,,  -going  ore,  203. 
Separation  of  slag,  13,  23,  45,  57, 

77,  91,  118,  207. 
Shingling,  23,  29. 
Shoot,  110. 
Shrinkage,  Allowance  for,  165. 

of  castings,  165,  166 
,,  ,,  ingots,  134. 

Siemens  appliances,  97. 
charge,  125. 

furnace,  59,  103-110,  255. 
plant,  97. 

process,  58,  59,  CO,  97. 
producer,  98. 
regenerator,  103,  105,  141. 
slag,  126. 

steel,  5«,  60,  61,  116. 
valves,  103. 
Silica,  7,  13,  26,  228,  229,  2.JO. 


XXIX 


Silica  bricks,  232,  233. 
Silicate  of  iron,  10. 

,,        ,,  manganese,  48. 
Silicates,  229. 

,,         Compound,  229. 
Silico-ferro,  see  Ferro-silicon. 

„     -spiegel,  236,  238. 
Silicon,  7, 8, 13,  48,  81,  134, 161,  236. 

,,       Increase  in,  48. 
Sill,  17,  110. 
Silver  sand,  232. 
Skull,  82. 
Slag,  126. 

„     ball,  212. 

„     Basic,  61,  95,  96. 

,,     Bessemer,  82,  83. 

basic,  95,  96. 

„     Blast-furnace,  18S,  211,  212, 
219,  220. 

,,      cement,  212. 

„      Disposal  of,  212. 

,,      Expulsion  of,  23. 

,,      for  furnace  lining,  114. 

,,      Grinding  of,  51,  96. 

„     heaps,  212. 

,,      indication,  124. 

,,     in  wrought  iron,  11. 

„      pocket,  107. 

„     Puddlers',  25,  177. 

„      Purifying,  131. 

„     Separation  of,  13,  23,  45,  57, 
77,  91,  118,  207. 

,,     Siemens,  126. 

„      Spoon  for  testing,  124. 

,,     tub,  118. 

„      Utilisation  of,  212. 

„     wool,  212. 
Sleeve,  68. 
Smoked  moulds,  46. 
Soaking  furnace,  140. 

pits,  138. 
Soda,  230. 
Softeners,  162,  238. 
Solid  bottom  cupola,  100. 

,,  producer,  100. 

Sow,  207. 

Spanish  ores,  178,  179. 
Spathic  ores,  177,  243. 
Specifications,  146. 
Spiegel-eisen,  49,  80,  235,  236,  237. 

Use  of,  119,  123. 
Spongy  iron,  22. 
Spray  tuyere,  194. 


Spring  heat,  40. 
Squeezer,  28. 
Stack,  16,  37. 

Blast-furnace,  207. 
Steel  cased,  16. 
Staff  hole,  17. 

Staffordshire  ores,  177,  179,  242, 
,,  pig  iron,  240. 

,,  tuyeres,  194. 

Steam  hammer,  30. 

,,      jet,  17,  98,  100. 
Steel,  35. 
„      Acid,  58,  61. 
,,      Annealed,  52. 
„      Basic,  58,  61. 
,,      Bessemer,  58,  59,  91. 
,,      Blister,  40,  47. 
,,      castings,  148,  165,  166. 
,,      Changes  induced  in,  51. 
,,  ,,        observable  in,  51. 

,,      Coarse-grained,  52,  53. 
,,      Crucible  cast,  35,  42,  47. 

ingot,  49. 

,,      Double  shear,  41. 
,,      Fiery,  134. 
,,      Fine,  52,  53. 
,,      Hardened,  52. 
,,      Hardening  defects,  55. 

of,  51,  53. 

Homogeneous,  42,  119. 
Honey-combed,  47. 
Inferior,  46. 
ingot,  Solid,  49. 
makers,  50. 
Martin,  58,  60. 
Medium,  119. 
melting  furnace,  42. 
„        holes,  42. 
,,       house,  42. 
Mild,  57,  78,  119,  125. 
Mushet's,  29. 
Normal,  52. 

Open-hearth,  see  Siemen*. 
Puddled,  49. 
Scorched  ingot,  46. 
Scrap,  121. 
Self  hardening,  49. 
Shear,  41. 
„      heat,  40. 

,,      Double,  40. 
,,          ,,         „     Single,  40. 
,,      Shrinkage  of  castings,  186, 
166. 


XXX 


INDEX, 


Steel,  Shrinkage  of  ingot,  134. 
„      Siemens,  58,  59,"  125. 
„  „         -Martin,  58,  60,  61. 

125. 

„      Single  shear,  41. 
,,      Special,  50. 
,,      Spongy,  46. 
,,      -through  heat,  40. 
„      Tool,  35. 
,,      Treatment  of,  51. 
,,      user,  50. 
,,      Weldable,  49. 
,,      Wild,  134. 
Stirlingshire  pig  it  on,  240. 
Stopper,  68. 

hole,  17. 
,,         notch,  17. 
Stoppering  ingot,  134. 
Stoves,  19ti. 

Cast-iron,  196. 
Cowper,  197,  19S.  190. 
Firebrick,  196,  197,  2<,0. 
Hot-blast,  196. 
Swedish,  19i>. 
Strength,  Crushing,  161. 
,,          of  cast  iron,  147. 
,,          ,,  malleable  iron,  146. 
„          ,,  mild  steel,  146. 
„  ,,  moulding   materials, 

149. 

„         Tensile,  161. 
,,          Transverse,  161. 
Stretching  force,  10. 
Stripper,  Hydraulic,  71. 
Stripping,  70,  71,  77,  1'20,  134. 
Sudden  cooling,  52. 
Sulphur,  8,  48. 

,,        beneficial,  8. 
,,        taken  up,  170. 
Swedish  bars,  35,  47. 

„        pig  iron,  35,  47,  48,  213. 


TAP  bars,  39. 

,,    cinder,  24,  25. 
Taphole,  114,  115,  118,  129,  132. 
,,         Making  up,  115. 
„         Opening,  115,  118. 
Tapping  furnace,  118,  207. 

side,  109,  110. 
Tar,  Anhydrous,  86. 
Teeming,  70,  120. 


Teeming,  Chilled  steel.  46. 
"Dead,  "46. 
holes,  46. 
Temperature,  Regulation  of,  44. 
Tempering,  55,  56. 
Tenacity,  10. 
Tensile  strength,  10,  143,  144,  146, 

161. 
,,  ,,         Calculation        of, 

144. 
Test  pieces,  142. 

„     sample,  90,  124.  130. 
Testing  cast  iron,  147. 
,,       machine,  142. 

steel.  142. 

Tetra-calcic  phosphate,  93. 
Thomas-Gilchrist  process,  63. 
Tie-rods,  103,  107. 
Tilting  Furnace.  103. 
Tinned  plates,  133. 
Titanic  oxide,  2t>,  230. 
Tool  steel,  see  Crucihle.  cant  steel. 
Tools,  Treatment  of,  51. 

,,      Quenching,  in  mercury,  54. 

,,  in  oil,  56. 

,,  ,.  in  water,  53. 

Toughness,  10. 
Transverse  strength,  161. 
Travelling  crane,  111. 

,,          engine,  111. 
Trays,  209. 
Treble  best  iron,  28. 
Tr.al  bars,  38,  39. 

,,     holes,  3S. 
Triple  compounds,  80. 
Trolley,  22,  23. 
Troughs.  209. 
Truck,  Cinder,  23 
Trunnions,  65,  110. 
Tungsten,  9. 
Tuyere  block,  195. 
Tuyeres,  Bessemer  acid,  65,  66. 
basic,  87,  88. 

,,         Blast  furnace,  194,  195. 
Cupola,  72,  73,  74,   150, 

153. 
Tyre  steel,  133. 


U 


UNPACKING,  190. 

Utilisation  of  gases,  220  221,  222. 
„          of  slags,  212. 


INDEX. 


XXXI 


VALUE  of  elements,  6,  7. 
Valves,  Butterfly,  103. 
Gas,  103,  107. 
,,        Mushroom,  103. 
,,        Reversing,  107. 
Vena  ore,  '243. 
Vertical  furnace,  140. 

hoist,  201. 
Vessel,  see  Converter. 


W 

WALLOON  method,  35. 
Water-balance  lift,  201. 

blocks,  195. 

bottom,  99,  100. 

cracks,  54. 

,,       Prevention  of,  54. 

in  fuel,  225. 

trough,  99. 
Welding,  10. 

Well  of  blast  furnace,  190. 
Wet  puddling,  11. 
W  heels  warf,  39. 
White  pig  iron,  216,  217,  241. 

„      (Belgian)  sand,  233. 
Wild  metal,  82,  i34. 
Wilson  producer,  98. 


Wire-drawing,  9. 

Wood,  204,  226. 

Wool,  Slag,  212. 

Working  Bessemer  acid  process  7$, 

76,  77. 
,,  ,,         basic      process, 

8i),  90,  91. 

blast  furnace,  203,  206. 
,,         cementation  process,  38, 

39,  40. 

crucible  process,  44-47. 
cupolas,  71,  72,  73. 
door,  17. 

,,         foundry  cupola,  156. 
hot- blast  stove,  200. 
kilns,  185,  186,  187. 
,,         puddling  furnace,  18-23. 
,,         Reheating,  furnace,   138, 

139,  140,  141. 
,,         Siemens     furnace,     acid, 

103-110. 
,,         Siemens    furnace,    basic, 

127-129. 

Wrought  iron,  11,  12,  47,  57,  146, 
147. 


YIELD  of  metal,  13,  24,  40. 
Yorkshire  best  iron,  34. 
„          pig  iron,  240. 


XXX11 


NAMES    MENTIONED. 


Avery,  Messrs.,  188,  189. 
Bannister,  C.  O.,  168,  170. 
Bell  Bros.,  188,  189. 
Bessemer,  58,  59. 
Blackwell,  George,  236. 
Brinnel,  52. 

Buchanan,  Robert,  vi,  153. 
Burnie,  K.  W.,  62. 
Cowper,  E.  A.,  197. 
Dolomieu,  85. 
Dutl,  A.  B.,  102. 
Firth  &  Sons,  36,  37,  104,  105. 
Foster,  William  J.,  195. 
Gilchrist,  P.  C.,  62. 
Gjers,  John,  138,  U6,  187. 
Ball,  John  W.,  138. 
Haibord,  F.  W.,  13S. 
Harrison,  Joseph  H.,  vi. 
Harvey,  Alfred,  vi. 
Hogg,  T.  W.,  237. 
Holgate,  T.  E.,  238. 
Holley,  Alex.  L.,  64. 
Huntsman,  35. 
Jones,  Wm.,  220. 
LilleshallCo.,  111. 
Lloyd,  F.  H.,  194. 
Martin,  E.  P.,  62. 
M'Neil,  Charles,  160. 
Metcalfe,  William,  50. 
Munnoch,  Peter,  240,  241. 


Mushet,  Robt.  F.,49. 

Osborn   &   Company,  42,  43,   100, 

110. 

Pourcel,  Alexandre,  236. 
Pretty,  W.  H.,  239. 
Richards,  E   Windsor,  62. 
Ridsdale,  C.  H.,  93. 
Riley,  James,  220. 
Royston,  G.  P.,  168,  170. 
Saniter,  E.  H.,  220. 
Seebohm,  Henry,  42. 
Sexton,  Prof  ,  vi. 
Scott,  C.,  149. 
Siemens,  Frederick,  59. 
Sir  Wm.,  58. 
Snelus,  George  J.,  62. 
Stead,  J.  E..  149,  101. 
Stevenson,  John  L.,  191. 
Stirling,  Rev.  Dr.,  97. 
Talbot,  Benjamin,  236. 
Taylor  &  White.  49. 
Thomas,  S.  Gilchrist,  62. 
Thwaites  Bros. ,  153,  155,  158, 
Tucker,  A.  E.,  13S. 
Turner,  Prof.,  56,  161. 
Waldron,  H.  W.,  51. 
Wilson,  Alfred,  100. 
Wilson,  G.  A.,  131. 
Wood,  Charles,  161. 


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